1: Atomic Structure and the Periodic Table

Proton
position, relative mass, relative charge

nucleus, 1, +1

Neutron
position, relative mass, relative charge

nucleus, 1, 0

Electron
position, relative mass, relative charge

orbitals, 1/1840 (negligible), -1

Atomic Number (Z)

The number of protons in the nucleus.

Mass Number (A)

The total number of protons and neutrons in the atom.

Isotopes

Isotopes are atoms with the same number of protons but different numbers of neutrons.

similar chemical properties (no. of electrons)
varying physical properties (mass/no. of neutrons)

Relative Isotopic Mass

The mass of one atom of an isotope compared to 1/12 of the mass of one atom of carbon-12.

Relative Atomic Mass

The average mass of one atom compared to 1/12 of the mass of one atom of carbon-12.

Relative Molecular Mass

The average mass of a molecule compared to 1/12 of the mass of one atom of carbon-12.