Ionisation energies

What is the unit of ionisation energy?

kJ/mol⁻¹

Ionisation energy of sodium

Why does magnesium have a higher ionisation energy than aluminium?

Because of their sub-shell structures

Electron configuration of magnesium

1s²2s²2p⁶3s²

Which orbital does the first ionisation energy remove an electron from?

3s orbital

Electron configuration of aluminium

1s²2s²2p⁶3s²3p¹

Which orbital does the first ionisation energy remove an electron from?

3p orbital

Which orbital is further away from the nucleus: 3s or 3p?

3p

Which orbital is higher in energy: 3s or 3p?

3p

How is the electrostatic attraction between the 3p orbital's electrons and the nucleus different compared to that of the 3s orbital's electrons?

The electrostatic attraction is lower

What does this mean in terms of ionising?

It is easier to ionise an electron in the 3p orbital than in the 3s orbital

What is Hund's rule?

Electrons will fill an unoccupied orbital before they pair up

Why is it easier to remove an electron from a doubly occupied orbital?

Because electrons in the same orbital repel each other

Explanation as to why the first I.E. of sulfur is lower than that of phosphorus

What are ionisation energies?

The energy value associated with removing one electron from the atom

When writing the ionic equation for ionisation energy of oxygen, do you start with O₂ or O?

O because you are dealing with purely atoms

Ionic equation for the ionisation of oxygen

O₍g₎ → O⁺₍g₎ + e⁻

What would be the second ionisation energy of oxygen?

O⁺₍g₎ → O²⁺₍g₎ + e⁻

What does the first ionisation energy mean?

The energy required to remove 1 electron from each atom of 1 mole of gaseous atoms to form 1 mole of gaseous ions

What is the definition of the second ionisation energy?

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

What three factors affect ionisation energy?

Nuclear charge, distance from the nucleus and shielding

What does a greater nuclear charge mean for removing an electron?

More energy is needed to remove the electron

How does an increased nuclear charge affect the ionisation energy?

Increases the I.E

What type of attraction is between electrons and the nucleus?

Electrostatic attraction

How does an increased distance from the nucleus affect the ionisation energy?

Decreases the I.E

What happens to the ionisation energy as the principle quantum number increases?

Decreases the I.E.

How does more shielding between electrons affect the ionisation energy?

Decreases the I.E

How does the first ionisation energy change down a group and why?

I.E. decreases because the atomic radius increases, making the electron easier to remove

What is another reason for the first ionisation energy decreasing down a group?

Going down a group there are more electrons between the nucleus and the outer electrons, making the outer electrons experience greater shielding

Ionisation energy for group 1

How does the first ionisation energy change across a period and why?

Increases because across a period the atomic radius decreases and the nuclear charge increases

Ionisation energy of period 3