Ionisation energy

Ionisation energy

The energy required to remove 1 mole of electrons from 1 mole of gaseous substance to form 1 mole of gaseous ion

First ionisation energy

The energy required to remove 1 electron from 1 mole of gaseous substance to from 1 mole of gaseous 1+ ion

Second ionisation energy

The energy required to remove 1 electron from 1 mole of gaseous 1+ ions to from 1 mole of gaseous 2+ ions

Third ionisation energy

The energy required to remove 1 electron from 1 mole of gaseous 2+ ions to from 1 mole of gaseous 3+ ions

Fourth ionisation energy

The energy required to remove 1 electron from 1 mole of gaseous 3+ ions to from 1 mole of gaseous 4+ ions

Relative Isotopic Mass

The average mass of an isotope relative to the 1/12 of the mass of an atom of carbon 12

Relative Atomic Mass

The weighed mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Ionisation energy factors: Nuclear charge (3)

The more protons there are in the nucleus, the more positive the nuclear charge is

The stronger the attraction is between the outer shell electron and the nucleus

The higher the nuclear charge, the higher the ionisation energy 

Ionisation energy factors: Atomic radius (3)

Electrostatic attraction reduces with increasing distance from the nucleus

An electron in a shell close to the nucleus will be much more strongly attracted than one in a shell further from the nucleus

The greater the atomic radius, the lower the ionisation energy

Ionisation energy factors: Shielding (3)

As the number of electrons between the outer electrons and the nucleus increases, the outer electrons have a weaker attraction to the nuclear charge

This reduction in the pull of the nucleus is due to inner electrons repelling the outer electrons

The more inner shells present, the lower the ionisation energy

Successive ionisation energy

The amount of energy required to remove 1 mole of electrons from 1 mole of gaseous substance successively

What happens to the ionisation energy in an element? (3)

As successive electrons are removed from the same shell, the ion becomes more positively charged

This increases the electrostatic attraction between the nucleus and remaining electrons

Therefore, ionisation energies increase progressively as you get closer to the nucleus

What does a large jump in successive ionisation energies mean? (2)

An electron is being removed from a new, inner shell closer to the nucleus

These electrons experience a stronger attraction to the nucleus and require more energy to remove

How can electron configuration be deduced from successive ionisation energies? (2)

Look for large jumps in ionisation energy

The number of electrons before the large jump is the number of electrons on the outer shell

How does ionisation energy change across a period?

Increases

How does ionisation energy change down a group?

Decreases