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Title: Grade 9 chemistry notes
Description: Detailed notes for grade 9 chemistry.
Description: Detailed notes for grade 9 chemistry.
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Chemistry Unit
The study of the structure and behavior of matter
...
An object falls to the ground every time
Inferences are conclusions based on observations (they
come from you)
Ex
...
Some things may be too big, too small, too far away to be
observed directly
In such cases the object’s behavior is observed instead of
the object
Ex (direct) - tape falling to the ground
Ex (indirect) - black hole with light bending around it
...
Ex
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(quantitative) – length is 2 cm, mass of 3
...
It may be expressed in words, a picture, mathematical
equation, or a physical representation
...
If it cannot explain new observations it needs to be
replaced with a new model
...
C
was the first person to propose the idea of the Atom
...
He concluded that everything in the world was made of
tiny particles which he named atoms from the Greek word
atomos
All matter is made up of atoms
...
Each element has its own atom with constant mass
3
...
Atoms cannot be created, destroyed or subdivided
1
...
To make compounds these atoms hooked
together
...
Specifically how electricity could flow
through elements and how they kept
charge
...
He discovered electrons by placing a positive source
near a Cathode Ray Tube
The particles were attracted towards it
...
From his experiments he was able to find the mass of
an electron:
9
...
AKA the Raison Bread Model
Thomson proposed that the Atom was a positively charged
porous sphere with negatively charged electrons embedded in
that sphere
...
Thomson’s model was abandoned when it could not
explain the results of Rutherford’s Gold Foil Experiment
...
Rutherford compared the deflection of these particles to
firing a bullet at a piece of tissue paper and having it
bounce back
...
The Atom is mostly empty space
2
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The Nucleus is positively charged
Rutherford’s Gold Foil Experiment handout
Atoms have a massive, positive core (nucleus) but are
mostly empty space containing electrons in a cloud
outside the nucleus
...
Since Planets do not fall into the sun even with gravity,
this could explain how electrons don’t fall into the
nucleus
...
It could also not explain the energy given off by plasma
...
It is the current Model of Matter
Proposed by Albert Einstein, Heisenberg and Schrodinger
States that the Atom contains a small, dense positively charged
Nucleus that contains both Protons and Neutrons
...
Electrons don’t have paths, only probable locations
...
Developing Models of Matter Handout
Questions handout
An element is a pure substance that cannot be broken
down into simpler substances
...
Eg oxygen is made up of only oxygen atoms
Today we have discovered 118 elements
Everything is made up of these elements
The names of elements have come from a number of
places
Examples
Phosphorus - named after the Greek word that means
“bringer of light” because the element phosphorus burns so
brightly
...
Uranium – Named after the planet Uranus (which was
named after a Greek god)
Bohrium – Named after Niels Bohr
People study Chemistry in all countries of the world in
hundreds of languages
Many have different names for the elements
To simplify communication in Chemistry, symbols have
been chosen for all the elements
These symbols are used all over the world
The system of naming symbols was first proposed by
Jacob Berzelius, a Swedish chemist in the 1800s
1
...
Use the first letter (upper case) and the second letter
(lower case)
( Ar – Argon)
3
...
Use the first or first and second letters from a foreign
language
(Au – Gold in Greek it is Aurum)
Some elements have three letters
...
Periodic table
Periodic table naming/symbol handout
Element research assignment
An element is a pure substance that cannot be broken
down into simpler substances and keep its chemical and
physical properties
...
Name
Charge
Location
Mass
Proton
positive
nucleus
Massive (1 amu)
Electron
negative
Outside
negligible
Neutron
No Charge
Nucleus
Massive (1 amu)
Elements are often described by how many protons and
neutrons they have
...
Carbon’s atomic number is 6 because each carbon atom
contains 6 protons
...
It is the average mass of an atom of the element and is
measured in Atomic Mass Units (amu)
The proton and neutron were discovered many years
before we had the technology to accurately determine the
mass of the particles
...
Therefore all mass came from the protons and neutrons
...
atomic mass
atomic number
Ex
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If we change the # of electrons we will create ions
...
also atomic mass A = p+ + no
or
A = Z + no
Isotopes are atoms which have the same number of
protons but different numbers of neutrons
...
pk/video/3428672/atoms-and-their-electrons
Or
https://www
...
com/watch?v=fhjwbVFCnqo
Although the Bohr model is not perfect, it is a useful way
for us to picture atoms and their fundamental particles
...
In the center is a
nucleus, which is made up of protons and neutrons
...
The first shell can hold a maximum 2 electrons and must
be filled before any electrons are placed in an other shell
...
(After this shell the Bohr model breaks down and becomes
too complex for grade 9)
In a proper Bohr diagram the electrons should be evenly
spaced
...
It will also lead us into Lewis
diagrams)
Aluminum
Carbon
During the time of Aristotle science did not progress very
quickly because hands on science was not popular
Since Dalton’s time much has been learned about
elements
...
Scientists try to find order in the things around them by
looking for patterns
...
He stated that the properties of elements are a periodic
function of their atomic masses
...
The atoms of the elements of a family each have the same
number of valence electrons
...
He knew there were gaps because he had found patterns in
properties
...
Properties of Potassium were similar to the properties
of Sodium and Lithium
He predicted that there were elements that must have
certain properties and that one day they would be
discovered
...
He concluded that the properties of elements are a
periodic function of their atomic numbers, not masses
...
Each
period represents an electron shell in the Bohr model
A group or family of elements is a vertical column in the
periodic table and is numbered from 1-18
older tables use two numbering systems IA – VIIIA for the
first 18 element families and IB – VIIIB for the others
The elements in a family have similar physical and
chemical properties and their atoms all have the same
number of valence electrons (exception –He)
Alkali Metals
Lithium Family
Alkaline Earth Metals - Beryllium Family
Chalcogens Oxygen Family
Halogens Fluorine Family
Noble Gases Helium Family
Hydrogen – is its own family
Bohr assignment
Mendeleev’s periodic table
more than 75% of the elements
They are normally:
Shiny
Generally silver-grey (except gold, and copper)
Malleable (can be flattened)
Ductile (can be stretched)
Solid at room temperature (except mercury)
Conduct heat and electricity
about 15% of the elements
They normally :
Have no lustre (not shiny)
Are brittle
Are non-conductors (except carbon/graphite)
Are solid or gas at room temperature (except Bromine)
...
Chemical reactivity of an element is determined by the
number of electrons in its valence shell
...
They will gain or lose electrons to fill their shells
...
All alkali metals have one valence electron
...
Likewise as we go down the family, the electrons are
easier to lose because the atoms become very large
...
They readily react with Halogens to form compounds in
1:1 ratios
Ex
...
Alkaline Earths need to lose two electrons, which is more
difficult than one, making them less reactive than the
alkali metals
React with Halogens to give compounds with ratios of 1:2
Ex
...
Halogens are very good at stealing electrons and therefore
they are highly reactive
...
As the atoms become larger they become less reactive
...
F2, Cl2, Br2, I2
Chalcogens are less reactive than the halogens because
they have two electrons missing from their valence shell
It is much more difficult to get two electrons than one,
therefore the reactions are relatively slower (still quite fast
though)
...
MgO, BeS
2:1 ratios with Alkali metals
...
Na2S, Cs2O
All noble gases have full shells and therefore are not
reactive
...
This is why it took many years to discover them, scientists
could not create anything different to be observed
...
This is because the first shell has only two electrons
...
It can also lose an electron, like an alkali metal(this
actually makes it a proton)
All matter is made up of extremely tiny particles
...
Pure substance
A substance made up of only one kind of particle
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gold, water , oxygen, table salt
...
How many letters are in the alphabet?
How many words in the dictionary?
Now
How many elements are there?
How many compounds can the elements make?
Most of the substances we know are made up of 2 or more
elements
...
Carbon dioxide, water, baking soda
a pure substance whose particles are made of two
or more different kinds of atoms
...
The particles of a compound are called molecules
A particle made up of 2 or more atoms clustered
together
...
The molecule is the smallest unit of a compound
...
He, Cu
Molecules of identical atoms Ex
...
It also tells us the number of atoms of each element
present
Monatomic
Helium (He)
Single atoms
1 atom Elements
Diatomic
Oxygen gas (O2) 2 atom molecule
Carbon
monoxide (CO)
Polyatomic
Can be elements
or compounds
Sulfur (S8)
Contain many
Water (H2O)
atoms
Elements and
compounds
Symbol for the
element oxygen
Symbol for the
element hydrogen
H2O
The small number here
means 2 atoms of hydrogen
No small number here
means 1 atom of oxygen
How many of each type of element are present in each
compound?
Al2O3
NH4OH
Ba(NO3)2
Cu3(PO3)2
Write the element symbol
...
Determine the number of electrons in the valence shell
according to its position in the periodic table
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Ignore all other previous shelled electrons
...
Draw the dots(electrons) around the element
1
...
Covalent bonds
Form between two non metals
electrons are shared between the atoms to form full shells
Br2
H 2O
NCl3
2
...
e
...
2
...
3
...
Ex
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Nitrogen will become nitride
...
We can ignore the subscripts for this year, they become
important next year
Title: Grade 9 chemistry notes
Description: Detailed notes for grade 9 chemistry.
Description: Detailed notes for grade 9 chemistry.