ionisation energy

what is ionisation energy?

The energy required to remove one mole of electrons from one mole of gaseous atoms

ionisation energy down a group

decreases

why does ionisation energy decrease down a group

number of protons increases (so nuclear charge increases), radius of atom increases, more shells so shielding increases

ionisation energy across a period

increases

why does ionisation energy increase across a period

number of protons increases so nuclear charge increases, creating a stronger attraction between nucleus and electrons, pulling them closer and reducing atomic radius, constant shielding

large increases of ionisation energy

shows removal of electron from a shell closer to nucleus

What is electronegativity?

ability of an atom to attract electrons towards itself in a covalent bond

electronegativity across a period

increases as atomic radius decreases and nuclear charge increases whilst shielding is constant

ionisation energy across group 2 and 3

dips as electrons in higher energy 2p oribital, further from nucleus so more shielding from 2s orbital

ionisation energy across group 5 and 6

dips as electron repulsion in 2p orbital, same shielding

why does the successive ionisation energy of an element increase

Removing the outer electron from an atom forms a positive ion

Removing an electron from a positive ion is more difficult than from a neutral atom

As more electrons are removed, the attractive forces increase due to decreasing shielding and an increase in the proton to electron ratio

Negatively charged electrons have a stronger force of attraction to the positive ion