Notesale: Turn your study into money

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Nucleus, middle of atom
- Made up of protons + neutorns
- Overall positive charge
- Almost whole mass of atom is from nucleus
- Small compared to whole atom
Electrons, move around nucleus
- Negative charge
- Tiny compared to nucleus, virtually no mass
- Size of orbit depends on size of atom
- Occupy shells
Number of protons = number of electrons
- Charge on electrons is same as protons but opposite
- Number of neutrons not fixed but usually a same as number of protons
Protons
- Heavy (1)
- Positively charged (+1)

Neutrons
- Heavy (1)
- Neutral (0)

Electron shells
- Electrons always occupy shells (energy levels)
- Lowest energy levels filled first
- 1st shell: 2
2nd shell: 8
3rd shell: 8
- Most atoms = outer shell not full = unstable (want to react)

Electrons
- Tiny (1/2000)
- Negatively charged (-1)

Electronic configuration of above atom = 2
...
5
3+1

Atomic masses rounded to nearest 0
...

- Double bonds stronger than single = triple bond stronger than double …etc
...
1 2
...
1 2
...
8
...
g
...
g
...
6
Divide by the Ar of each element
9
...
4
Multiply by 10
4 :
Divide by 4
1 :
Simplest formula = 1 atom of Mg + 1 atom of O = MgO

O
6
...
4 / 16 = 0
...
pf atoms (of chosen element) x 100
Mr (of whole compound
% Composition
- Percentage (by mass) of each element in a compound
Actual yield = experiment yield
% yield = actual yield
x 100
Theoretical yield
Calculating mass
- Write out balanced equation
- Identify given elements
- Find number of moles of given elements
- Look at ratios of moles in equation + scale
- Use m = n x Mr to find mass of unknown

Theoretical yield = calculated from balanced equation

n = m/Mr

E
...
How many moles is 64g of methane CH4
Mr = 12
1 x4
16
n = 64
16
n = 4 moles

n = number of moles
m = mass
Mr = formula mass



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