Chemistry Unit 1 (just notes)

Same number of protons & electrons, different number of neutrons.

The average mass of all isotopes compared to the mass of an atom of carbon-12.

Atomic number: protons + neutrons

Proton number: protons (same as electrons)

A mole of a substance is defined by the amount of substance that contains as many particles as atoms in 12g of carbon-12 (Avogadro's constant).

The number of atoms in 12g of carbon-12: 6.02 x 10^23

Number of moles = mass in grams / molar mass in g/mol

mol = g / ram

Sum of all the relative atomic masses of the atoms in one molecule.

The mass of ONE MOLE of a substance (g/mol) - Relative atomic mass.

1 mole of any gas occupies 24 dm^3  at 25ºC and 1 atm (298K).