Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Chapter 4
Atoms and
Elements
Elements
• Remember, elements are the building blocks of all
matter
...
• All known elements are organized into a table
called the Periodic Table
...
2
Periodic Table of the Elements
3
Names of the Elements
• Each element has a unique name
...
(“hydro”
– Carbon is derived from Latin
...
4
Element Symbols
• Each element is abbreviated using a chemical
symbol
...
• Most of the time, the symbol is derived from the
name of the element
...
5
Element Symbols
How many elements are in each compound?
AlPO4 !
Na3N
!
FeCO3 !
Other Element Symbols
• For some elements, the chemical symbol is derived
from the original Latin name
...
– Selenium (Se)
– Bromine (Br)
– Xenon (Xe)
– Gold (Au)
8
Types of Elements
• Elements can be divided into three classes:
1
...
Nonmetals
3
...
5)
9
Metals, Nonmetals, and Semimetals
• Metals are on the left side of the periodic table,
nonmetals are on the right side, and the semimetals
(also called metalloids) are in between
...
2) All atoms of an element are identical and have the
same properties
...
4) Compounds contain atoms in small whole number
ratios
...
11
Dalton’s Atomic Theory
• The first two parts of Dalton’s theory were later
proven incorrect
...
• Dalton’s theory was an important step in the
further development of atomic theory
...
• Three subatomic particles were discovered
...
– Positively charge protons, p+
...
• An electron has a relative charge of -1
• A proton has a relative charge of +1
...
13
Structure of The Atom
• Protons and neutrons
are located in the
center of the atom
called the nucleus
...
14
Structure of The Atom Cont’d
• Each element has a
different combination
of protons, electrons,
and neutrons
...
69 x 10-24g which
is a very small number if expressed in g (grams),
The unit “amu” was created to make it easier to
describe the relative mass of subatomic particles
...
(amu)
16
Periodic Table
• The periodic table shows the atomic number,
symbol, and atomic mass for each element
...
This is the atomic number,
Z
...
• We use atomic notation to display the number of
protons and neutrons in the nucleus of an atom:
18
Using Atomic Notation
• An example:
• How many protons does sodium have?
• How many total protons and neutrons are there?
• How many neutrons are there?
19
Using Atomic Notation
• Here’s one more example: 238
92
U
• How many protons does uranium have?
• How many total protons and neutrons are there?
• How many neutrons are there?
Using Atomic Notation
• What does figuring out the # number of protons of
an atom tell us about the # of electrons in that
atom?
Since all atoms are electrically
neutral……
...
• Most elements occur naturally with varying
numbers of neutrons
...
• Isotopes have the same atomic number, but
different mass numbers
...
– Cobalt-60 is
– Carbon-14 is
60
27
Co
C
• How many protons and neutrons does an atom of
mercury-202 have?
14
6
– The atomic number of Hg is 80, so it has 80 protons
– Hg-202 has (202 – 80) = 122 neutrons
25
Using Atomic Notation
State the number of neutrons in an atom of each of
the following isotopes:
a)
15N
b)
58Ni
c) Iodine-131
d) Hydrogen-3
e)
52Cr
26
Simple & Weighted Averages
• A simple average assumes the same number of
each object
...
• A weighted average is calculated by multiplying
the percentage of the object (as a decimal number)
by its mass for each object and adding the numbers
together
...
• Copper has two isotopes:
– 63Cu with a mass of 62
...
09% abundance
– 65Cu with a mass of 64
...
91% abundance
• The average atomic mass of copper is:
62
...
6909 = 43
...
928 amu x 0
...
07 amu
63
...
985 amu
24
...
70%
10
...
983 amu
11
...
• Mendeleev is the architect of the modern periodic
table
...
32
The Noble Gases
• The periodic table was expanded by one group at
the far right of the periodic table with the
discovery of argon in 1894
...
• They were originally called the inert gases
...
33
Refined Arrangement
• In 1913, it was discovered that the nuclear charge
increased by one for each element on the periodic
table
...
• Recall, that atomic charge is due to the number of
protons in the nucleus, the atomic number
...
Properties of Metals
• Metals are typically solids with high melting
points and high densities and have a bright,
metallic luster
...
• Metals can be hammered into thin sheets and are
said to be malleable
...
36
Properties of Nonmetals
• Nonmetals typically have low melting points and
low densities and have a dull appearance
...
• Nonmetals are not malleable or ductile and crush
into a powder when hammered
...
37
Metals vs
...
a)
b)
c)
d)
e)
f)
g)
Shiny liquid at 500° C
Low melting point
Ductile
Reacts with metals
Dull powder
Reddish liquid (at room temp)
High density
38
Groups & Periods of Elements
• A vertical column on the periodic table is a group
or family of elements
...
• There are 18 groups and 7 periods on the periodic
table
...
• The first period has only 2 elements, H and He
...
• It is a gas with properties similar to nonmetals
...
41
Groups on the Periodic Table
• There are 18 groups on the periodic table
...
– IA is Li to Fr
– IIB is Zn, Cd, Hg
– IIA is Be to Ra
– VA is N to Bi
Chapter 6
42
Groups on the Periodic Table
• In 1920, the International Union of Pure and
Applied Chemistry (IUPAC) proposed a new
numbering scheme
...
– Group 1 is Li to Fr
– Group 2 is Be to Ra
– Group 12 is Zn, Cd, Hg
– Group 15 is N to Bi
Chapter 6
43
Groupings of Elements
• There are several groupings of elements
...
• The transition elements are in the B groups
(groups 3 – 12)
...
They are also referred to as the
rare earth elements
...
45
Common Names of Families
• Several columns of the periodic table have
common, trivial names
...
The alkali metal in the 6th period:
2
...
The metal in Group VIIB/7 and Period 4:
4
...
• For example, table 6
...
• We can predict the properties of potassium based
on the other alkali metals
...
227
63
...
10
• We can predict that the atomic radius of K is in
between 0
...
248 nm, that its melting point is
in between 97
...
9 0C, and that its atomic mass
is in between 22
...
47 amu
...
• All of the alkali metals have oxides of the general
formula X2O:
– Li2O, Na2O, K2O, Rb2O, Cs2O, and Fr2O
...
What is the formula for the chloride of barium?
– The general formula is XCl2, so the formula must be
__________
...
• Sometimes these two numbers are not equal and
there is a difference in the total positive charges
(protons) and total negative charges (electrons) in
the atom
...
• Therefore, an ion is any atom with a net charge
...
• If we remove an electron from an atom, that atom
has an overall charge of +1 and is called a cation
...
54
Ions Cont’d
Ex) Ions of Silicon
+
+
+
Ions Cont’d
• What is the atomic structure of the following ions?
a) Be2+
b) N3-
Atomic Number = 4 which means 4 protons
Atomic Mass = 9 which means the total number of
protons and neutrons adds
up to 9
Therefore 9 – 4 = 5 neutrons
A neutral Be atom has 4 electrons, but this ion has
a charge of +2, which means 2 electrons were
removed
...
56
Ionic Charge
• Metals tend to lose electrons (form cations)
...
• Semi-metals (metalloids) can lose or gain electrons
depending on the circumstances
...
57
Summary
• Atoms are composed of protons, neutrons, and
electrons
...
• Atoms are mostly empty space
...
58
Summary Cont’d
• All atoms of the same element have the same
number of protons
...
• The mass number for an isotope is the total
number of protons plus neutrons
...
59
Summary Cont’d
• The elements in the periodic table are arranged by
increasing atomic number
...
• The periodic table can be broken down into
– groups or families which are columns
– periods or series which are rows
Assigned Readings and
Homework
• Read pages 95–115 (skip page 110) in textbook
...
jlab
...
html
61