First Ionisation Energy

What is the definition of the first ionisation energy

The energy required to remove one electron from each atom in a mole of atoms in a gaseous state

What are the 3 factors affecting the first ionisation energy?

• nuclear charge

• Atomic radius

• Electron shielding

How does the nuclear charge affect the first ionisation energy?

The greater the number of protons the greater the nuclear charge, the greater the nuclear charge, the greater nuclear attraction

What is nuclear attraction?

The force of attraction between the nucleus and the outermost shell

How does atomic radius affect nuclear attraction?

As the atomic radius increases, nuclear attraction decreases

what is electron shielding

The inner shells of electrons repelling the outer shell because they are all negative

Why does first ionisation energy decrease across a group?

Due to more electron shielding from having more shells

Why does first ionisation energy increase across a period?

Because the nuclear charge increases from having more protons and nuclear attraction therefore increases as well, requiring more energy to take an electron

What are the first pair of irregularities in the first ionisation energy table?

Beryllium and Boron

Why does Boron have a lower ionisation energy than beryllium?

Boron as an electron in its 2p orbital which is higher in energy than one in a 2s orbital which beryllium only has up to so less energy is needed to remove an electron from a 2p orbital

Why is oxygens first ionisation energy lower than nitrogens

Oxygen has a paired electron in the 2p orbital while nitrogen only has one. There is more repulsion between the two of oxygens electrons so less energy is needed to remove the electron