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2nd secondary

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Chemistry
Second Secondary

2nd secondary

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Contents
Chapter One:
Atomic structure
...
youtube
...

https://www
...
com/watch?v=hePb00CqvP0

Chapter Three:
Bonds and forms of molecules
...
youtube
...

https://www
...
com/watch?v=-0N1ZZZRM48

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General objectives of chapter one:
1-Recognize the historical background of atomic structure
...

3-Discuss the Rutherford’s atomic model
...

5-Define the reasons of inadequacy of Bohr’s model
...

7-Explain the concept of electron cloud and orbitals
...

9-Distribute electrons of any atom considering the building
up principle and hund’s rule
...


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Chapter one

Structure of the atom
Atomic structure
1-Democritus’s (Greek philosophers) idea:
Any piece of matter can be divided into smaller parts and each part can be
subdivided into smaller parts which can't be divided this part is called Atom
...

b- He supposed that all matters composed of 4 constituents which are (water,
air, dust and fire) and postulated that the cheap metals such as iron or copper
can be changed into precious ones like gold by changing the percentage of four
constituents
...

B-He was the 1st scientist to define the element as pure simple substance which
Cannot be analyses into simple one by normal chemical methods
...

2- Every element consists of very small dense atoms which can’t be divided
...

4- Atoms of different are different
...


5 – Thomson’s model of the atom:
The scientist Thomson carried out many experiments on the electric
discharge through gases from which he had discovered the cathode rays
...


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Cathode- rays experiment
(Discovery of the electron)
High voltage 10000
vollts

Anode

Cathode
To vacuum pump

a- All gases under normal conditions of pressure and temp
(76 cm
...
25c) don't conduct electricity
...
These rays were named by (Cathode rays)
...

2) Transfers in straight lines glowing the glass facing the cathode
...

4) Have a thermal effect
...

6) Cathode rays don’t change by changing either cathode material or type
of the gas, which proves that cathode rays take part in the structure of
all substances
...


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Metal sheet covered
with ZnS

Gold foil
Source of alpha
particles

1– He allowed alpha particles to hit a metallic plate lined with Zinc sulphide
(glows when hits with alpha rays)
2– On placing a gold foil in the front of alpha rays he concluded the
following from the following observation
...

1- A very small percentage of alpha
particles reflected back to
appears as flashes on other side of
sheet
...


2- Most of the atom is a space not
solid as explained by Dalton
and Thomson
...

4- The dense parts of the atom,
which concentrate in it most
mass, have same charge of
alpha particle (+ve) which
called nucleus of the atom
...


1- The Atom:
Although it has very small size but it has a complicated structure that
resembles the solar system in which electrons revolve around the
central nucleus in orbits as planets revolve around the sun
...
Located in the centre of the atom with
(+ve) charge
...
Most mass of the atom is
concentrated in the nucleus as mass of e is very small and can be
neglected
...

2- No of electrons (-ve) equals no of protons (+ve) so the atom is
electrically neutral
...

b- Centrifugal force due to velocity of electron around the nucleus
...

Explain: Structure of the atom in the view of Rutherford
...

2- Atom is electrically neutral as no of p+ s equals to no of e's
...

4- Electrons orbit the nucleus in a rapid movement without gaining or losing
energy
...


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6- Each electron in the atom has a definite amount of energy depending on
the distance between is E
...
This energy increases as its radius
increases
...
Each level has energy expressed by a completely no called principle Q
...


Ex: The 1st E
...
no = 1
The 2nd E
...
no = 2
8- If when atom is excited by heating (Quantum) or by electric discharge
the electron will transfer to a higher E
...
The excited electron in the higher E
...


 Remarks:
1- The quantum: Is the amount of energy gained or lost when an electron
jumps from one E
...

2- The difference in energy between levels (Q) is not equal i
...
the difference in
this energy decreases further from the nucleus
...

3- The electron does not move from its level to another unless the energy
absorbed or emitted is equal to the difference in energy between 2 levels i
...

one quantum
...
Q can't be divided or doubled

Give reason: It is wrong to say that e' to be transferred from E
...
L (M)
needs amount of energy equals 2 quantum
...
L to higher ones
...

2- He introduced the idea of quantum no to detect energy of electrons in
energy levels
...


Disadvantages (Inadequacies) of Bohr's theory:
1 – If failed to explain the spectrum of any other element even that of He
except hydrogen (Simplest Electronic System)
...

3– He postulated that it is possible to determine precisely both speed and
location of an electron at the same time
...

4– He described the electron when moving in a circular planer orbit, which
means that hydrogen atom is planer
...


Bohr's Theory
The atomic spectrum
Studying and explaining the atomic spectrum was the key to his atomic
structure in 1913 and he was deserved Noble Prize in 1922
...

2 – By using spectroscope we find that this light consists of a fixed number of
colored lines called line spectrum
...


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By exp
...


N
...


The principles of Modern Atomic Theory:
1 – Dual nature of electron
...

3 – Finding the mathematical expression, which describes the wave motion
of electron, its shape and its energy?
-------------------------------

1 – The dual nature of the electron
The experimental data showed that the electron has a dual nature i
...

a) It is a material particle
...


* De Broglie principle:
Every moving body (such as electron or the nucleus of an atom or whole
molecule) is associated with (accompanied by) a wave motion (or matter
waves) which has some properties of light waves
...
We can only say that it is
probably to a greater r lesser extent to locate the electron in this or in that
place
...

3
...

 The electronic motion around nucleus has wave properties therefore the
position to use the term electron cloud to describe any orbital
...
"
 The difference between the orbit and orbital concepts according to both
Bohr and the wave mechanics theories:
Bohr s theory
Schrodinger s wave mechanics theory
 It is a circular planer orbit with
 It is an electron cloud used to
particular radii
describe any orbital
 Electron cloud the regions of
high density of dots represent
the region of high probability of
finding the ( e ) from which it is
Bohr's orbit
possible to define the atomic
radius
Probabili
ty of
finding
the
electron

Schrodinger's wave mechanics
theory

Distance from
the nucleus
R

Probabilit
y of
finding
the
electron
Distance from the
nucleus

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 The mathematical solution of the Schrodinger equation introduced four
numbers which are called quantum numbers
...
Besides, they define the energy, shape
and direction of orbital
...
no (n)
...
no (ℓ)
...
no (mℓ)
...
no (ms)
...
levels their number in the heaviest known atom in
the ground state is seven
...
level = two times the square of
the level no (2n2)
...
L
K
Is filled with
2 electrons
nd
-2 E
...
L
M
Is filled with
18 electrons
th
-4 E
...
However,
the atom becomes unstable if no of electrons exceeds 32 electrons on any
level
...
Subsidiary Q No (ℓ):
1- Used to detect the no of sub levels in each E
...

2- The energy sub levels take the symbols s, p, d, f
...
When he used a spectroscope, which has a high resolving
power, he found that the single line (which represents electron transition
between two different energy levels) is indeed a number of fine spectral
lines which represents electron transition between very near energy
levels (sublevels)
...


-1st E
...
L
-3rd E
...
L

K
L
M
N

has 1 sub level
has 2 sub level
has 3 sub level
has 4 sub level

1s
2s, 2p
3s, 3p, 3d
4s, 4p, 4d, 4f

N
...
level is not equal
...
levels also differ in energy
...


Ex: 4d>3d

4p>3p>2p

 There is a small difference in the energy between sub-levels
...
Magnetic Q No (m):
Detected by Zeeman when he exposed spectral line to strong magnetic field, he
found that each line divides into many lines, so he concluded that each E
...


- Magnetic Q No(mℓ ) is characterized by:
1- Used to detect no of orbitals in each E
...

2- Sublevel (S) has one orbital of spherical symmetrical shape
...

 Each orbital (Px,Py,Pz ) is perpendicular to the other two
...
e point of zero electron
y
density
...

5- Sublevel (f) has 7 orbital
...

Ex: px = py = pz
7- No of orbitals in each E
...
level = n2
...
No (ms):

 Detects the direction in which the electron spins around its axis during its
rotation around the nucleus
...

 It has only two possible values + 1/2 – 1/2




Give reason: Each orbital carries 2 electrons although they are negatively
charged
...
L, sub levels
orbitals and no of electrons:
1- No of energy sublevels = order of principle level (n)
...

3- No of electrons occupying a given E
...


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Ex:
Order of E
...


E
...
These rules are:
 Pauli’s exclusion principle : it states that:
 It is impossible for two electrons in the same atom to have the same four
quantum numbers
...

Ex: 4s is filled before 3d as energy of 4s < 3d
...
"

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Ex:
8O

2
2
3
7N 1s – 2s – 2p

px py py
2p   
2s 

1s 

1s

2s


1s2 – 2s2 – 2p4

2p


px


py


py


 Atom is stable when the outer sub-level is half completely filled with e's
...

2- Electrons prefer to be paired with another electron than to transfer to a
higher sub-level, as the energy needed to transfer it to a higher sub-level
...

Other E
...
Write short notes on:
1- Hund's rule
...

3- Heisenberg uncertainty principle
...
Write scientific term:
1- Area of space around nucleus which has probability for finding electron
...

3- Sublevel can be saturated with 10 electrons
...
number which detects no of orbitals and their direction in space
...
number used to detect direction of electron around its axis
...
Complete:
1- Max
...
The electrons can be distributed in
…………
...
levels …………
...
orbitals
...
In energy
...
and ………
...
Give reason:
1- It’s wrong to consider the electron as (-ve) particle only
...

3- The relation 2n2 cannot be applied to O, P and Q levels
...

5- Sub level d is filled with 10 electrons
...

(First question):

20

A- Choose the correct answer:
1- The energy sublevels that form the third energy level are --------a- s

b- s, p

c- s, p, d

d- s, p, d, f

2- The uncertainty principle was proposed by-----------------a- Heisenberg
...

C- Rutherford
...


3- The --------elements tend to reach the electron structure : ns2 , np6
a- Main transition
b- inner transition
c- noble

d- transition

B- Give reasons:
1- The atomic radius in the same group increases as the atomic number increases
...

C- Write the electronic configuration for 20 Ca by two different ways and show
the location of element in modern periodic table
...
(---------------)
2- The limited colored lines obtained from heating gases to high temperature under
low pressure
...
(-----)
4- The tendency of an atom to attract the electrons of the chemical bond to itself
...


(Third question):
A- Compare between:
1- The acidic oxides
...
Hund's rule
...

2- Electron affinity
...
6A° and the bond length of hydrogen
fluoride molecule equals 0
...


B- Show by an experiment how you can obtain the cathode rays
...

2- Arrange the energy sublevels according to building up
principle
...

4- Define the location of the four blocks of the table
...

6- Compare between the electron affinity and
electronegativity
...

8- Identify the relationship between the atomic radius and
the acidic and basic properties
...

10-Calculate the oxidation number
...


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Chapter two
Classification of elements and the long periodic table
The long form periodic table:
It depends on the building up principle (Aufbau) the elements are arranged in
an ascending order according to their atomic number (each element have one
electron more than the element before it)
...

2- P – block consists of (6) groups because the P – sublevel consists of three
orbitals which filled with six electrons
...

4- f block are separated from the table so that the table is not too wide (long)
5- The first period contains two elements because it consists of elements of
the sublevel 1S = 2 electrons
...

7- The third period contains eight elements because it consists of element of
sublevel (3S + 3P) = (2 + 6) = 8 electrons
...

9- The fifth period contains (32) elements because it consists of elements of
the sublevels (5S + 4d + 5P) = 2 + 10 + 6 = 18 electrons
...

How can you find the location and the type of element in the periodic
table?
1- Write the electronic configuration of element in quantum levels
...

Example:
Find the number of period and group for each of the following element:
Na: The atomic number = 11
Cl : The atomic number = 17

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Noble gases: They are the elements of the last column of the P – block all
their energy levels are completely filled with electrons
...

The transition elements: They are the elements of the d – block all their
energy levels are completely filled with electrons except for the two external
energy levels
...


Trends and periodicity of properties in the periodic table
The atomic radius:
We can not determine the atomic radius because electron has a wave motion
so it is impossible to determine exactly the location of an electron around the
nucleus
...

B

Rad
ius
A
B Ra

diu
sA

The bond length: It is the distance between the nuclei of two bonded atoms
...


2- Electron diffraction
...
98 Å and the
length between carbon and chloride atoms C – Cl is 1
...
Calculate the
atomic radius of carbon
...
98
‫ــــ‬
2

= 0
...
76 – 0
...
77 Å

3- The bond length in the molecule of NH3 is 1
...
6 Å
...
6‫ـــ‬
2

= 0
...
3 = 0
...
7 × 2 = 1
...

Atomic radius increases in group by increasing of atomic number why?

Because the increase in atomic number makes to increase the number of
energy level screen the attractive force of the nucleus for valence electrons
and increase the repulsion force between electrons therefore the atomic radius
increases
...
B
...

2- The anion's radius is bigger than that of its atom?
This is due to the increase in the number of the negative charges in the shells
therefore the repulsive force between the electrons increases so the shells
move a part and this leads to increasing of the anionic radius than that of its
atom
...
It has a
positive value (∆H = + ve KJ/Mole)
...

3- The ionization energy of element of group (5A)
( N7 – P15 – As33 – Sb51 – Bi83 ) is much greater than any element have the
same period because the outer most energy sublevel (P) has three electrons
and it is half filled with electrons ( nP ) and this gives the atom of the element
some extra stability so the ionization energy is greater
...


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5- Ionization energy increases period?
Because the positive nuclear charge gradually increases with the increase of
the atomic number led to decrease the atomic radius and increase the attractive
force of the nucleus on the valence electrons therefore the electrons needed m
large high energy to remove (separated) from the atom
...

7- The ionization energy of elements of group (2A) is much greater than
any element have the same period?
Because the outer most energy level (S) of the element of group (2A) is
completely filled with electron (nS2) and this gives the atom of the element
some extra stability so the ionization energy is much greater
...
R
...
In the horizontal periods electron affinity increases with the
increase in atomic number?
Due to the atomic radius (size) gradual decrease so it becomes easier for
the nucleus to attract the new electron
...
R
...
The electron affinity decreases in group?
Due to the increase of the atomic volume with increase atomic number and
this leads to the screening of the attraction force of the nucleus on the valence
electrons
...


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Elements of the fifth group (N7 , P15 ) have a lower value of electron
affinity
Because the outer most energy sublevel (nP ) has three electrons and it is half
filled with electrons it gives the atom some extra stability ( N7 : 1S2 , 2S2 ,
2P2)
...

Electron affinity of Fluorine ( F9 ) is less than that of chlorine ( Cl17 ) ?
Because the atomic radius ( size ) of fluorine atom is smaller than that of
chlorine atom and when fluorine atom gains electron it is affected by a great
repulsion force bigger than that in chlorine atom and fluorine atom is very
small size
...


Compare between ionization energy, electron affinity and electro
negativity
Ionization energy
It is the amount of
energy
needed
to
remove
the
least
connected
electron
bond in a single atom

Electron affinity
It is the amount of
energy released when
an extra electron is
added to a neutral
single atom to form an
ion
It refers to the atom in It refers to the atom in
its single state
its single state

Electro negativity
It is tendency of an
atom to attract the
electrons of chemical
bond to itself

It refers to the atoms
which linked together
in the molecule
It
is
inversely It
is
inversely It
is
inversely
proportional to the proportional to the proportional to the
atomic radius
atomic radius
atomic radius

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The
atom
losses
electrons and converted
into positive ion
It has a positive value

28

The
atom
gains
electrons and convers
into negative ion
It has a negative value
∆H = - value
type of reaction is
exothermic

Differentiation between metal and non metal
Metals
Non metals
Valence shell has less than help its Valence shell has more than half its
capacity of electrons ( 1 or 2 or 3 ) capacity of electrons ( 5 or 6 or 7 )
They one called electropositive They are called electronegative
elements
...

electricity
...
B
...

2- Metals are considered as electropositive elements because metals lose
electrons to form positive ions
...

4- Metal are good conductors of electricity because they have few valence
electrons which can transfer easily from one position to another in the metal
structure
...


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6- Metals have small values for ionization energy and electron affinity
because they have large atomic radius
...


Metalloids
1- They are elements whose valency shell contains 4 electrons
...

3- They act as semiconductors (Boron – silicon) which are used in or
transistors and knows as semiconductors electronic instruments
...

od

Metals

Metalloids increase in period because the atomic size decrease and the
attractive force of nucleus to electron will be increased therefore it becomes
easier for the nucleus to gain a new electron
...

In groups : non metals decrease because the increase in the atomic number
makes to increase the energy level and screen the attractive force of nucleus
on the valence electrons therefore it is difficult for the atom to gain a new
electron
...


Metallic prop inc

Nonmetallic prop dec

Nonmetallic prop inc
Metallic prop dec Strongest non metal

Strongest metal

Acidic – basic properties
Acidic oxides
They are non – metallic oxides
such as CO2 , SO2 , SO3 , P2O5
They dissolve in water to form
acids
Co2 + H2O
H2CO3
SO2 + H2O
H2SO3
SO3 + H2O
H2SO4
P2O5 + H2O
2H3PO4

Basic oxides
They are metallic oxides such as
Na2O , K2O , MnO , CaO , BaO
Some basic oxides dissolve in
water to form alkalis and others
are not
Na2O + H2O
2NaOH
K2O + H2O
2KOH
CaO + H2O
Ca(OH)2
MgO + H2O
Mg(OH)2
They react with alkalis to form They react with acids to form salt
salt and water
and water
CO2 + 2NaOH
Na2CO3 + H2O Na2O + 2Hcl
H2O + 2Nacl
SO2 + 2NaOH
Na2SO4 + H2O MgO + H2SO4
MgSO4 + H2O
They do not reaction with acids
They do not react with alkalis
The strength of the oxygenated acids: They are acids that contain hydrogen,
oxygen and a third element usually a non-metal
...

(n) Is the number of oxygen atoms?
(m) Is the number of hydroxyl groups?

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The strength of oxy acids are depends on the number of oxygen atoms which
does not linked with hydrogen atoms when this number increase, the strength
of the acid
...

2-They have both acidic and basic properties such as Al2O3 , ZnO , Sb2O3 ,
SnO
...

The modern definition:
valence shell of the atom
...
g
...
g
...

The oxidation number of hydrogen in its hydrides = -1 such as NaH , KH ,
CaH2
...

Such as NaCl , HCl , CuSO4
The oxidation number of any element in its pure state = zero
...
g
...

The oxidation number for any atomic group ( poly atomic ion ) = the number
of charge on the group ( ion ) such as OH- , SO4-- , CO3-- , NH4+ , PO4---
...

The Reduction process: it is the process of gaining electrons due to decrease
the oxidation number for the element
...

C2H5OH
C = -2

CH3CHO
C = +1

CH3COOH
CO2
C = zero
C = +4
Oxidation
Oxidation
Oxidation
Explain the type of change (oxidation or reduction) that of chromium and
iron in this reaction
...

The oxidation number of the elements in groups from IV to VII = the group
number = - value because the elements gain electrons to complete a full shell
...


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Questions on Chapter 2
A- Complete the following:
1- The formula of sodium peroxide is ……… and the oxidation number of
oxygen in it is
...
, and the oxid
...
of Beryllium is

...
and the oxid
...
of
nitrogen in it is …………
...
But in
superoxides is ……
...

4- The oxidation number of hydrogen in most of its compounds is
...

5- The decrease of atomic radius of nonmetals leads to the
...

B- Write the scientific term (or rule which explains each of the following
statements:
1- Half the distance between the centers of two similar atoms in diatomic
molecule
...

3-The energy required to separate electrons less in connection by single atom
in gaseous state
...

C- Choose the best answer:
1- The sublevel (d) contains
...
electron
...

(2 - 3 - 5)
3- The valency shell of the atoms of fifth group elements contain
...
block
...

a) 6
b) 16
c) 14
d) 32
6- The fourth energy level is saturated by a number of electrons equals
...

a) Up on increasing atomic number only
b) Up on decreasing atomic number only
c) Up on increasing atomic volume only
d) A and c
8- The oxidation number of hydrogen in hydrogen molecule is (1, 2, 3, 0) and
its oxidation number of hydrogen chloride is (1, 2, 3, 0)
...

a) +2
b) +l
c)-2
d)-l
10- The oxidation number of oxygen in H 2O2 is
...

a) Less
b) more c) the same
d) none of the above
-13- The oxidation number of Sulphur in (SO4) is
...

a) Increasing of atomic number only
...

c) Increasing of boiling degree
...


C- Write the scientific explanation of the following:
1
...

2
...


2nd secondary

37

3
...

4
...

5
...


it

is

impossible

to

measure

the

atomic

radius

6
...

7
...

8
...

9
...

10-Zinc oxide is called amphoteric oxide
...

2- Define shapes of molecules on the view of valence’s
electron pairs repulsion theory
...

4- Recognize the electronic theory of valency
...

6- Recognize the formation covalent bond in hydrogen and
hydrogen fluoride molecules on the basis of the valence
bond theory
...

8- Explain the overlap of hydrogen and carbon orbitals to
form methane molecules
...

10-Define the donor and the acceptor atoms in the
coordinate bond
...
Because their outer energy levels
are completely filled with electrons (stable elements) where they have
high I
...
& low E
...

 On mixing iron fillings with Sulphur the result will be a mixture not a
compound
...

But if this mixture is heated enough to form new bond the result will be a
compound called iron sulphide FeS
...

3) Co-ordinate bond
...


B-Physical bonds:
1) Hydrogen bonds
...


1)Ionic bond:
- This bond is usually formed between metals and nonmetals
...

Accordingly, their ionization energies are low
...
Metal atoms are then changed
to cations with an identical electron structure to the nearest noble gas in
the periodic table
...

Accordingly, their electron affinities are high this facilitates the gaining
of electrons (those lost by metal atoms)
...

- Consequently, an electrostatic attraction occurs between (+ve) cations &
(-ve) anions
...

- This means that ionic bond has no materialistic existence
...
N between
them is higher than 1
...
N
...


Na

Mg

Electro negativity
Different in
Electronegativity
Melting point ( C)
Boling point( C)

0
...
09=2
...
2
Mgcl2
3-1
...
8
714
1412

Conductivity of
electricity

Very good
conductor

Good
conductor

Al
1
...
5=1
...


(2) Melting and boiling points:
- Ionic compounds generally have high melting and boiling points because
a great amount of energy is needed to break down the crystal lattic and
overcome the strong electrostatic attraction force between cation and
anions
...
N
...
7 it occurs by sharing of valence electrons
and is divided into two types:

1- Pure covalent:
Formed between 2 similar atoms have the same E
...
N =
Zero)

Ex:

F2, Cl2, O2, H2
- In this case, the two atoms have the same E
...
(same ability to attract the
pair of electrons to itself)
...


2- Polar covalent:
- Formed between 2 atoms have difference in E
...
7

Ex: HCl molecule
- In this case, because chlorine atom has more E
...
, so it has greater
ability to attract the pair of electrons of the covalent bond (i
...
the
electrons spend more time at a chlorine atom)
...

Polar molecules:

2nd secondary


H



N


H



H
Ammonia (NH3)

42

H





O



H


Water (H2O)

H

CL

Hydrogen chloride

General properties of covalent compounds:
1) Electrical conductivity:
- Ions are responsible for electrical conductivity in solutions
...


2) Melting and boiling points:
- Covalent compounds are characterized by their relatively low melting &
boiling points due to the very weak attraction force between their
molecules which needs low amount of thermal energy to be separated
...


Answer: Because HCL is a polar covalent compound which can diffuse in
Benzene (non- Polar solvent) but can't be ionized into (+ve) ion (H+) & (-ve)
ion (CL-), so it:
Can’t conduct electricity
...

HCL + H2O

H3O + + CL -

Explanation of covalent bonds:
(1) Electronic theory of valency: (Octet rule Theory)
- Lewis and kosel scientist supposed that:
“All atoms of elements have tendency to reach the octet structure of the
outer energy level for the nearest inert gas expect hydrogen, lithium, and
beryllium"

Example:

2nd secondary

43





H

  Cl   Cl 







N

H


H


 Defects of electronic theory of valency:
(1) It failed to explain the binding in many molecules
...

Cl 

  Cl
P

Cl 



Cl

  Cl

(ii) In BF3:
Boron is surrounded by 6 electrons
...

Give reason: Octet rule can't be applied for PCI and BF3
...
B
...
)
- Electrons has wave property so the formation of covalent bond as a result
of overlapping of an atomic orbital of an atom with an unpaired electron,
with another orbital in another orbital in another atom has an unpaired
electron to form a molecular orbital contains a pair of electrons
...

py
1s2 – 2s2 – 2p5

9F
1H

1s1

px py pz
2p   
1s 
2s 
1s 

pz
px

1
s

3- NH3 molecule:
H1: 1S1
N7 1S2 , 2S2 , 2P1x, 2P1y , 2P1z
 NH3 is formed as a result of overlapping of
Px , py ,pz Orbitals of (N) atom with 3(1S) orbitals of hydrogen atoms
...
So, the carbon atom must have
4 single electrons
...

- Now, the carbon atoms has 4 single electrons, but they aren't equivalent
in energy as one electron is located in 2S orbital which is lower in energy
than 2P orbital
...
How?? By hybridization

2nd secondary

45

between one orbital of 2S and 3 orbitals of 2P forming 4 orbitals
equivalent in shape and energy
...
These orbitals must go as far a part as possible from the other
orbitals to decrease the repulsion forces between orbitals
...
To complete
the methane molecule, the four equivalent electrons of the four
hybridized orbitals of the carbon atom can overlap with the 4(1S)
electrons of the 4 hydrogen atom
...

(2) Angle between bonds: 109
...

(4)Bonds: Single covalent bond of the type sigma
...


How does the valence bond theory explain the structure of methane?


2p2  


2s2
1s 
Carbon atom in
the ground state
2

  2p3
 2s1
 1s2
Excited
carbon atom

2nd secondary

46




sp3
5

109 /28

sp3


sp3 sp3



1s2

Hybridized carbon atom

C

sp3
3

sp3

sp

H

sp3


H

H
 Hybridization:
"It is the process of the overlapping between two different orbitals or more
of the same atom to produce a number of new orbitals called hybridized
orbitals
...

(2)Hybridization occurs after excitation
...


Example:
Hybridization of 1S with 1P gives 2SP orbitals
...

Hybridization of 1S with 3P gives 4SP3 orbitals
...

(5) The shape of the hybridized molecular orbitals differ from these of the
pure atomic orbitals forming them
...


Molecular Orbital Theory: (M
...
T)
- Considers the molecule as one unit (or a big atom with multi – nuclei) in
which some of atomic orbitals of the combined atoms overlap forming
molecular orbitals
...

atomic orbitals side by side
...

same axis ( same line )
3- Collinear overlap
...

4- Strong due to great orbital
4-weak due to less orbital
overlapping (high electronic overlapping (low electronic density)
...

5- Between(a)pure – hybridized 5- between pure – pure orbitals
...
g
...
g
...

molecule
...

(4) Bonds: di – cover bond of the type sigma and pi
...
{ sigma }
- {C C} formed due to overlapping of pure 2pz orbital of a c atom with
another 2pz orbital of another C atom
...
{ sigma }
2
1s2 sp2sp2sp 2pz

2
2pz sp2sp2sp2 1s

2nd secondary

H
Sp

48

pz

pz

2
5

021

Sp2 Sp2

C

H

Sp2
C

Sp2

Sp2

H

H

Explain acetylene molecular structure:
(1) Type of hybridization: sp
(2) Angle between bonds: 180◦
(3) Stereo structure: linear structure
...

- { C C } formed due to overlapping of one sp orbital of c atom
With one sp orbital of another C atom
...
{Sigma}
- {C C} formed due to overlapping of one 2py orbital of C atom
With another pure 2py orbital of another C atom {pi}
- {C C} formed due to overlapping of one pure 2pz orbital of C
Atom With another pure 2pz orbital of another C atom {pi}

py

pz

5

sp

H

C

py
081

sp sp

C

pz
sp

sp sp

z
py p

H
-

_

2nd secondary

49

Point of
comparison

Methane
CH4

ethylene
C2H4
( ethane )

No and type of
Hybridization
Angle between
bonds
Stereo structure

1s+3p=4sp3
109o 28

1s+ 2p =
3sp2
120o

Tetrahedron
pyramid

Planer
triangle

Acetylene
C2H2
( ethane )
1s +1p = 2sp
180o
Liner

VSEPR theory:
Electron pairs (free or bonded) are distributed in the space around the central atom
of the molecule, where the repulsion between them is the minimum to form the most
stable shape of the molecules
...


Example:
(1) Hydronium ion (hydroxonium) H3O+
Is formed when a strong acid dissolved in water:

(Donor)

(Proton acceptor)

(Hydronium ion)

H
H

O

H + H
+

H

H

Give reason: proton of strong acid does not exist freely in water
(3) Ammonium ion (NH4+):
-in the last example , proton is acceptor while central atom is donor like
oxygen in H3O+ , phosphorous in PH 4+ & nitrogen in NH4+
...


2nd secondary

50

Q: compare between covalent and co-ordinate bonds
...


IV – Hydrogen bond:
*is a bond formed between polar molecules in which hydrogen atoms lies
between to atoms of high Electronegativity as ( oxygen ) or ( fluorine ) , so
the hydrogen atom binds with one atom by polar covalent bond and binds
with the second atom by hydrogen bond
...


Explanation of hydrogen bond in water:
(1) Oxygen atoms has small volume, so it has high Electronegativity (3
...
1
...

(2) Hydrogen bond is formed due to the attraction force between one
hydrogen atom of one molecule and one molecule and one oxygen atom of
another molecule, so molecule of water are collected by hydrogen bonds, so
water exists in a liquid state and has high boiling point
...


Answer: Due to the presence of big difference in E
...
between hydrogen and
oxygen
And so formation of hydrogen bond between molecules of water
...


Answer: Due to formation of H2 bond between hydroxyl group of sugar & oxygen
of
H2O, but its solution is a bad conductor of electricity because it can't be
Ionized
...

2- H-Bond is longer than covalent bond
...

4- H-Bond has several forms:
A- Straight line
...


B
...

Strength in (k
...

H2 Bond
3A
21

V- Metallic Bond (between atoms of metal in the metallic
structure):
"Is formed from electron cloud of the free valence electrons around (+ve)
metal ions
...
The strength of the metallic bond
depends on no of free valence electrons
...


2nd secondary

52

Give reason: elements of group IA as Na are soft and have low melting point
While elements of group IIIA as AI are hard and have high melting point
...


 Explain types of bond in the following:
Nacl
molecule
Iron
Fluoride

water
Aluminum

Hydronium ion
Ammonium chloride

Chlorine
Hydrogen

 Note:
 Ionic compounds dissolve in polar solvent (H2O)
...


2nd secondary

53

Questions
(1)Define each of the following:
1- Ionic bond
...

3- Chemical reaction
...
Octet rule theory can't be applied for PCL5 or BF3
...
The pi-bond is weaker than sigma bond
...
HCL solution in water conducts electricity but its solution in benzene
does not conduct electricity
...
Ionic compounds have higher melting point than covalent compounds
...
NaCl molten is a good conductor of electricity while AlCl3 solution is a
poor conductor of electricity
...

2- A bond is formed by the overlapping of orbitals head to head
...

4- The bond in which the pair of electrons arises from one atom
...

(4) Compare between:
1
...

2
...

(5) Explain types of bonds in:
- Hydrogen chloride HCL
...

- Acetylene
...

B) Polar covalent compound
...

2- What will happen by combination between A&C then dissolving the
result in water and put a litmus paper?
(7) Choose the correct answer from the following:
1
...

c) A combines with B
...

d) A reacts with C
...
An elements has atomic number 9
...

c) Ionic
...

d) Covalent
...
Covalent compounds are characterized by:
a) Weak intermolecular
forces
...


attractive

b) Good
electrical
conductivity
...


4
...

c) Electron affinity
...

d) Ionization potential
...
Hybridized (sp) molecular orbitals will have:
a) Three orbital lobes
...


b) Two orbital lobes
...


6
...

b) Between the two carbon atoms there is a triple bond, one is sigma and
two are pi
...

d) B and c are correct
...


20

(First question):

A- Define the following:
1- Ionization potential

2- Octet rule
...

2- The angle value between covalent bonds in ammonia molecule is less than that in
methane molecule
...


(--------)

2- An ion is formed from the combination of water molecule with a positive hydrogen ion
...


1- The type of hybridization, the value of angles & Stereo structure
...
Atomic radius
(Fourth question)

2- Metallic bond

What is the atomic number for element in period 2, group 6A?

2nd secondary

56

Chapter 4
General objectives of chapter 4:
At the end of this chapter, the student should be able to:
1
...

2
...

3
...

4
...

5
...

6
...

7
...


2nd secondary

57

The main group elements of the periodic table
1- S – Block elements: elements of group I Alkali metals
...
A
First: elements of S – Block
Elements of (1A) group:
Elements of (1A) group are considered as alkali metals because their oxides
dissolve in water easily forming strong Alkalis
...
6 H2O )
...

B- Oxidation number in their compounds is equal (1+)
...

D- The first ionization energy low while second ionization energy is high
because in the first ionization energy it is easy to lose the valency
electron but the second ionization energy result from the breaking up
of a completely filled shell
...


2nd secondary

58

3- They are very strong reducing agent because they have a large atomic
radius (or volume) and small ionization energy so they lose the
electrons from their outer most energy level easily
...

5- They have a large atomic radius because each element occupied the
beginning of its period
...

7- Potassium and Cesium are used in photoelectric cells because the
atoms of these elements have a large atomic radius and small
ionization energy so when they are exposed to light they lose the
electrons from their outer most energy level easily
...

Sodium is kept under kerosene because it is a very active metal which
can react with air and water so it is stored under kerosene
...


2nd secondary

59

* Reaction with nitrogen of air to form (give) lithium nitride
...
R
...

Li3N + 3H2O
NH3 + 3LiOH
9- Reaction with water
2 Na + 2H2O
2 NaOH + H2 + E
Sodium reacts with water forming sodium hydroxide and large
amount of energy which is enough to cause the burning of hydrogen
evolves with an explosion so sodium fires are not extinguished by water
...

Elect
Na H
Na + + Hrolys

is

Go towards cathode

Go towards anode

N
...


2nd secondary

60

13- Reaction with halogens:
All elements of group 1A are reacts with halogens forming very stable
ionic halides
...

Li2CO3

He
at

Li2O + CO2

16- Action of heat on metals nitrates:
They decompose partially giving metal nitrite and oxygen
2NaNO3

∆

2NaNO2 + O2

Sodium nitrate is not used in the manufacture of bombs because a great
explosion happens when potassium nitrate decomposes by heat
2KNO3

∆

2KNO2 + O2

Extraction of metals
Alkali metals are not found in elemental state in nature because these
metals are easily to losing their valence electron and oxidized in
atmospheric air forming the oxide
...

Anhydride: Compounds which dissolve in water giving acid or alkali
...
p
...
p
...
10H2O is known as washing soda
a) preparation :
1- in laboratory : by passing CO2 gas through a hot solution of
NaOH , the solution is left to cool , white crystal of Na2CO3 are
separated
2NaOH + CO2
∆ Na2CO3 + H2O
2- in industry : (Solvay method)
NH3 + CO2 +NaCl + H2O
2NaHCO3

∆

NaHCO3 +NH4Cl

Na2CO3 + CO2 + H2O

Properties:
1- White powder, easily dissolves in water
...
e
...

Phosphor P15 : non – metal – Calcium phosphate ( Ca3(PO4)2) Apatite
CaF2Ca3(PO4)2 (4 atom)
...

2- With oxygen: All elements of this group form oxides are acidic
(decreases with increasing the atomic number) such as N2O3, N2O5,
P2O3, P2O5 while other are amphoteric Sb2O3 or Bi2O3 or basic
(increases with increasing the atomic number) Bi2O3
...

NH3 + H+OHNH4+ OH- The polarity of hydrogen compounds in this group decreases with
increasing atomic number
...

Both nitrogen (gas) and bismuth (metal) have not allotropic
...

Black – grey – yellow
...


Nitrogen N2
Preparation of nitrogen gas in the lab
...

NaNO2 + NH4Cl
∆
NH4NO2 + NaCl
NH4NO2
∆
2H2O + N2
By adding:
NaNO2 + NH4Cl
NaCl + 2H2O + N2

Properties of nitrogen
1- Reaction of nitrogen with hydrogen
Ele
N2 + 3H2 ctri
2NH3
c
spa
2- Reactionrkof
Ele
N2 + O2 ctri
c
arc
...

2NO + N2
2NO2
3- Reaction of nitrogen with metals
3Mg + N2

∆

Mg3N2
Magnesium nitride
Mg3N2 + 6H2O
2NH3 + 3Mg (OH) 2
∆

2nd secondary

66

4- Reaction of nitrogen with calcium carbide (CaCN2) to form calcium
Cyanamid (CaCN2) is used as agricultural fertilizer because it reacts
with water irrigating to from ammonia gas fertilizer
...
H2SO4 in not used for during
ammonia gas because it reacts with acid forming
(NH4)2SO4 due to the basic property of ammonia
...


Properties of NH3 gas
1- It is colorless and pungent smell
...

NH3 + H2O
NH4OH
*Experiment to prove that NH3 gas is soluble in water and its solution has
alkaline effect
...

(The fountain experiment)

2nd secondary

67

G
...
F: Ammonia is considered anhydride base?
Preparation of ammonia gas in industry (Haber's method)
From nitrogen and hydrogen in presence of catalyst (Fe, Mo) at 500ºC
under 200 atmospheric pressure
...

The temperature of exp
...

Properties of acid:
1- Action of heat:
It decomposed by heat giving nitrogen dioxide (NO2), oxygen and
water
4HNO3 ∆
4NO2 + O2 + 2H2O
2- Nitric acid is an oxidizing agent because it is reduced in to different
product depends on:
a- The activity of reducing agent (the metal)
...

c- Concentration of the acid
...

2Fe + 8HNO3 Dil

2Fe (NO3)3 + 4H2O + 2NO

- Metals below hydrogen in chemical series
...
e
...

The above reaction is used to differentiate between dil
...
HNO3:
3Cu + 8HNO3

Experiment
1- Put a piece of
copper to each of
them
...

Dil
Cu + HNO3
Cu(NO3) + 2NO +
2H2O

Conc
...

Con
Cu + 4HNO3
c
Cu(NO3)2 + 2NO2 + 2H2O

The passivity effect : Some metals (such as Fe – Cr – Al ) are not affected
by the concentrated nitric acid (HNO3) due to the formation of layer of
the metal oxide and this layer is non porous so it protects the metal from
further reaction
...


Phosphorus: The manufacture of matches, - fire work - phosphorus
fertilizers, many alloys such as phosphorus bronze (Cu + Sn +
P) which is used in manufacturing of pushing fans in ships
...

Antimony: It is used with lead in the acidified car batteries – used for
manufacturing of instruments of detecting the infra-red rays
...


2nd secondary

70

Questions
Show by symbolic equations only:
1
...

3
...

5
...

Passing of CO2 gas on a hot solution of NaOH
...

Exposing a piece of sodium in air for a long time
...


How can you get each of the following?
1
...

2
...

3
...

4
...
Nitric acid
...
Ammonia gas from nitrogen
...
The Chemical reactivity of the alkali metals
...
Potassium superoxide is used submarines and high altitude aero planes
...
We must not extinguish sodium fires with water
...
Cesium metal is used in photoelectric cells
...
The weak strength of the metallic bond between atoms of 1st group metals
...
Ammonium ion is more basic than phosphonium ion
...
There are various oxidation numbers for nitrogen
...
A co-ordinate covalent bond in ammonium ion is formed
...
Calcium Cyanamid is used as a fertilizer
...
Sodium is kept under kerosene
...
And dilute H N O 3
Give one use for:
1- Cs
2- Potassium Nitrate
3- Phosphorus
4- Caustic soda
5- Washing soda

2nd secondary

71

Note

2nd secondary

72

Note



---