Atomic Structure

No. of orbitals in each subshell

S: 1

P: 3

D: 5

F: 7

Hund’s rule

When filling a sub-shell, each orbital must be occupied single before occupied in pairs

Configuration of Chromium and reason

1s2 2s2 2p6 3s2 3p6 3d5 4s1

Half-filled 4s and 3d sub-shells are more stable

Configuration of Copper and reasoning

1s2 2s2 2p6 3s2 3p6 3d10 4s1

A completely full 3d subshell is more stable

What is a free radical

A species with one or more unpaired electrons

Definition of the first ionisation energy

The amount of energy required to remove one electron in one mole of gaseous atoms

What affects ionisation energy?

Atomic radius: When this increases, less energy required

Nuclear charge: When this increases, more energy required

Shielding: When this increases, less energy required

Trend of ionisation energy down a group

• Increasing atomic radius due to increasing number shells of electrons

• Increased effect of inner shell electrons shielding the outer shell electrons

Trend of ionisation energy across a period

Ionisation energy increases due to increasing nuclear charge and decreasing atomic radius.

Little change in shielding effect due to more successive electrons being added to the same quantum shell

Exceptions of trends across a period

Al & Mg / Be & B / Na & Ne: Outermost electrons Increasing in Al is 3p1 – less energy required to remove and experienced better shielding

S & P / O & N: Sub-shell is singly filled in P, and S has paired electrons in one orbital to give inter-electron repulsion