Made up of
subatomic particles
electrons, neutrons
and protons. Relative
mass and charges of
1,1,1/2000, 1+, 0, 1-,
respectively.
Mass Number (on top) no.
of protons and neutrons in
the nucleus of an atom.
Atomic Number (on the
bottom) numbers of
protons.
Neutral atoms
number of protons
and electrons same.
For negative ions
electrons more than
protons and other
way round for
positive ions.
Isotopes: same number of
protons but a different number of
neutrons. Same chemical
properties. Slightly different
physical properties i.e. density or
rate of diffusion.
2. Atomic Models
1. Thomson's Model:
Experiments made him
conclude that atoms weren't
solid and indivisible. Came up
with Plum pudding model-
positively charged sphere with
negative electrons or
"corpuscles" embedded within.
2. Rutherford Model: Fired
alpha particles at an extremely
thin gold sheet. Most passed
straight through and some
deflected backward -
disproving the plum pudding
model. New model, the nuclear
model positively charged
nucleus where most mass is
concentrated and cloud of
electrons. Most of the atom
found to be empty space.
3. Changes of Rutherfords
Model: Discovered
protons, explained different
charges in the nuclei.
Rutherford predicted they'd
also be other particles to
make the nuclei heavier,
these were discovered by
James Chadwick - the
neutron.
4. Bohr Model: Four main
changes: Electrons existed
in fixed orbits. Each shell
has a fixed energy. When
electron more between
shells electromagnetic is
emitted or absorbed.
Radiation has fixed
frequency because energy
levels are fixed. This
explained by Noble Gases
were inert and other trends
in reactivity.
3. Relative Mass
Relative
Atomic Mass:
the weighted
mean mass of
an atom of an
element
compared to
the mass of
1/12 of the
mass of an
atom in carbon
12
Relative Isotopic
Mass: the mass of
an atom of an
isotope compared to
the mass of 1/12 of
the mass of an atom
in carbon-12
When calculating
relative atomic mass:
Add: percentage of
abundance x mass
number, together and
divide by 100. On mass
spectrum? Multiply
each relative isotopic
mass by it's abundance
and the divide by sum
of abundances.
Relative
molecular
mass and
formula
mass is the
same: add
up all Ar's
in
compound.
Only
difference
is formula
is for ionic
compounds
as they
aren't
made of
molecules.
4. The Mole
Number of particles in a
mole is the Avogadro's
Constant (Na) which is 6 x
10 to power of 23.
Molar
mass is
Mr but
when a g
mol -1
stuck on
the end.
Number of Moles = mass of substance / molar mass
5. Concentration Calculations
For Liquids: Number of Moles = Concentration x Volume (in dm3)
For Gases: Number of Mole = Volume (in dm3) / 24
6. Formulas
Empirical
Formula: Smallest
Whole Number
Ratio of Atoms in
a Compound.
M - Mass
M - Moles
R- Ratio
(MMR)
Molecular Formula:
Actual Numbers of the
atoms in a molecule.
1. Find the Empirical Mass by adding
all Mrs in Empirical Formula. 2.
Divide the Molecular Mass by the
Empirical Mass. 3. Multiply the
empirical formula by the number found
from previous step.
7. Calculating Formulas
Empirical Formulas from experimental data:
1. Moles = mass / Mr to find out the amount of
moles per product made. 2. Use this to find out
the moles of each atom you began with. 3.
Write down the ratio of moles. 4. Divide to get
a whole number ratio. 5. YOU HAVE AN
EMPIRICAL FORMULA.
Empirical Formulas from percentage
compositions: Just convert % to grams.
Molecular Formulas from experimental data: 1. Moles =
mass / Mr to find out the amount of moles per product
made. 2. Use this to find out the moles of each atom you
began with. 3. Write down the ratio of moles. 4. Divide to
get a whole number ratio. 5. Work out the mass of the
empirical formula. 6. Divide the molecular mass by
empirical mass. 7. Multiply the number from previous
steps by the empirical formula.
8. Balancing Equations
You're an A-level student you should be able to do this, nevertheless, you can only
add numbers to whole compounds on full equations. In ionic equations balance the
charges by adding electrons and make sure their is the same number of atoms on
each side.
9. Equations and Calculations
Calculating Masses: 1. Write out a balanced question. 2. Work out how many moles of the reactants you
have. 3. Use the molar ratio from the balanced equation to work out the number of moles of product that
will be formed from this much reactant. 4. Calculate the mass of that many moles of product.
Calculating Gas Volumes: 1.
Write out a balanced question.
2. Work out how many moles
of the reactants you have. 3.
Use the molar ratio from the
balanced equation to work out
the number of moles of
product that will be formed
from this much reactant. 4. Put
these numbers in a gas volume
equation.
State Symbols: a = solid, aq = aqueous, l=liquid and g = gas.
10. Acids, Bases and Salts
Acids are proton donors and Bases are proton acceptors.
H+ (aq) + H2O (l) ---> H3O+ (aq)
this a hydroxonium ion that has
formed.
Release of H+ ions equations: H2SO4
(l) + water ---> 2H+ (aq) SO4 2- (aq) &
HCl (l) + water ---> H+ + Cl-
General Formulas for different types of
reactions: Acid + Base = Salt + Water,
Metal Oxide + Acid = Salt + Water,
Metal Hydroxide + Acid = Salt + Water,
Metal + Acid ---> Metal Salt +
Hydrogen & Metal Carbonate + Acid =
Metal Salt + Carbon Dioxide + Water
11. Anhydrous and Hydrated Salts
Water in lattice is called water of
crystallisation. A solid containing
water of crystallisation is hydrated.
A salt is anhydrous if it doesn't
contain any water of crystallisation
First you find the mass of
water lost by taking the mass
of the anhydrous salt away
from the mass of the hydrated
salt. Then you find the
number of moles of water
lost. Next find the number of
moles of anhydrous salt that's
produced. Now you look at
the amount of moles of
anhydrous salt to moles of
water. you scale down to 1:n
and round off.
12. Titrations
Allows you to find out exactly
how much acid is need to
neutralise a quantity of alkali.
Method: Measure you alkali
using a pipette and put it in a
flask along with some
indicator. Add acid to the alkali
using a burette. Add a bit at a
time. Swirl to make sure it's
all mixed properly.
Indications: methyl orange -
turns yellow to red when
adding acid to alkali.
phenolphthalein - turns pink to
colourless when adding acid
to alkali.
When calculating concentrations or volume
rearrange the following equation: Number of
Moles = Concentration x Volume (in dm3)
13. Oxidation States
14. Redox Reactions
OIL RIG
Oxidising agent gets reduce and a reducing agent gets oxidised.
Oxidation states of an
element tell you how many
electrons it has accepted or
donated. Here are the
rules: Uncombined
elements: 0, Monoatomic
ion: same as it's charge.
Neutral compound it's 0,
Combined Oxygen is -2 but
in peroxides it's -1,
Combined hydrogen +1
expect hydrides where it's
-1 and H2 = 0.
Systematic names: oxidation number is the value of attached roman numeral.