Key
Formulas
These are the key formulas (and other quick methods) that you really
need to know:
Name 
Formula 
Moles in solids 
OR 
Moles in gases 

Moles in liquids 

Concentration of a liquid 

Relative atomic mass 
 Multipy atomic mass by abundance of each isotope.
 Add products together.
 Divide by 100.

Empirical Formula 
 Write down elements present as headings.
 Write down the mass of each beneath.
 Work out the moles of each (divide mass by Ar)
 Divide all mol values by the lowest mol value.
 Ratio up or down to get whole numbers.

Molecular Formula 
 Work out mass of empirical formula.
 Divide molar mass by new mass.
 Times empirical formula by this new number.

Ionic Compounds 
 Swap the numbers around.
 Ignore any 1s.
 Ignore equal numbers.

First ionisation energy 
Mg(g) > Mg(g) +
e 
Second ionisation energy 
Mg(g) > Mg²(g) +
e 
Electron arrangement 
1s² 2s² 2p3s² 3p4s² 3d,
4p 














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