Formulae, Equations and Amounts of Substance

The nucleus is made up of protons, neutrons.

Electrons occupy the space outside the nucleus. 

Protons have a positive charge.

Electrons are negative.

Neutrons have no charge. 

A substance that cannot be broken down chemically into a simpler substance, 

Number of protons in the nucleus. 

This is equal to the number of electrons. 

Number of protons plus the number of neutrons. 

Atoms with the same number of protons and electrons, but a different number of neutrons.

Have different physical properties. 

Always have the same chemical properties. 

s - solid

l - liquid

g - gas

aq - solution in water

The average mass of its isotopes compared with the mass of an atom of the carbon-12 isotope. 

The amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12

The number of atoms in exactly 12g of carbon-12 is found from experiments to be 6.02 x 1023

In a compound, the sum of the relative atomic masses of all the atoms in the chemical formula. 

One mole of any gas occupies 24dm3 at 25 degrees C (298K) and 1 atmosphere pressure. 

The simplest formula for a compound, showing the whole-number ratio of the number of atoms of each element present. 

Percentage by mass = mass of solute / mass of solution x 100

Percentage by volume = volume of one component / total volume x 100

Concentration = mass of component / mass of solution x 1000000

Can be useful for very low concentrations. 

Crystals that contain different salts in a 1:1 ratio. 

Crystals that contain different salts in a 1:1 ratio. 

Percentage yield = ^{actual yield}∕_{predicted yield} × 100

Mass of atoms in desired products / mass of atoms in reactants x 100