Chapter 1 Keywords and Principles A Level Chemistry Edexcel

Atomic number

Number of protons in an atoms = Z

Mass number

Number of protons and neutrons in the nucleus = A

Relative Atomic Mass

Ar = average of the masses of the atom compared to 1/12th of the mass of a carbon-12 atom

Relative molecular amss

Mr = sum of relative atomic masses of the atoms present in the formula of a molecule/compound

Relative isotopic mass

The mass of an individual atom of a particular isotope relative to 1/12th of the mass of an atom of carbon-12.

Isotopes

Atoms of the same element that have different numbers of neutrons but the same number of protons

VIADD

Vaporisation, Ionisation, Acceleration, Deflection, Detection - process of the mass spectrometer

Quantum shell

Defines the energy level of an electron

Orbital

Region within at atom that can hold up to two electrons with opposite spins

Hund's rule

Electrons occupy orbitals singularly before pairing takes place

Pauli Exclusion Principle

States that two electrons cannot occupy the same orbital unless they have opposite spins

Aufbau principle

An electron occupies the lowest-energy orbital that can receive it

Order of electron orbitals

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

1st ionisation energy

Energy required to remove an electron form each atom in one mole of atoms in the gaseous state

Lithium flame colour

Red

Sodium flame colour

Yellow/Orange

Potassium flame colour

Lilac

Rubidium flame colour

Red/purple

Caesium flame colour

Blue/violet

Beryllium flame colour

No colour

Magnesium flame colour

No colour

Calcium flame colour

Brick red

Copper flame colour

Blue

Strontium flame colour

Crimson red

Barium flame colour

Apple green

S-block element

An element that has the highest energy electron in a s-orbital

P-block element

An element that has the highest energy electron in a p-orbital

D-block element

An element with a d-orbital in the outer quantum shell

Periodicity

A regular repeating pattern of atomic, physical and chemical properties with increasing atomic number