2. First Ionisation Energy

Question 1

Define the term first ionisation energy.

Answer 1

the energy needed to remove one mole of electrons from one mole of gaseous atoms

Question 2

what is the equation for the first ionisation energy of oxygen?

Answer 2

O(g) —- O+(g) + e- , 1st ionisation energy: +1314kJmol-1

Question 3

what does a high ionisation energy mean?

Answer 3

there will be a strong attraction between the electron and the nucleus ,so more energy is needed to overcome the attraction and remove the electron.

Question 4

How does a larger Nuclear Charge affect the ionisation energy?

Answer 4

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction. First ionisation energy will be higher.

Question 5

How does a larger Atomic Radius affect the ionisation energy?

Answer 5

The larger the atomic radius, the further away the electrons are from the nucleus and so there is a weakened attraction. This will decrease first ionisation energy.

Question 6

How does shielding affect the ionisation energy?

Answer 6

The more shielding there is, the more shells there are from the nucleus so lower attraction. The first ionisation energy will decrease.

Question 7

Explain the trends in ionisation energy as you go DOWN a group in the periodic table.

Answer 7

-ionisation energies generally fall
- atomic radius increases and so reduces attraction.
-shielding also increases and so reduces attraction to the nucleus.
- Nuclear charge does increase as you go down, increasing attraction(though this is overridden by the others.

Question 8

Explain the trends in ionisation energy as you go ACROSS a period in the periodic table.

Answer 8

-general trend is for the ionisation energy to increase.(not always)
- nuclear charge increases, higher attraction
-smaller atomic radius, higher attraction
-shielding does NOT change due to the same shell.