Ionisation Energies

Question 1

What is an ionisation energy ?

Answer 1

Evidence for how the electrons are arranged in atoms comes from ionisation energies

Question 2

Definition of 1st ionisation energy

Answer 2

The energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions

Question 3

What is the 2nd ionisation energy ?

Answer 3

The energy required to remove the second electron only not both the 1st and 2nd

Question 4

What are the three factors that affect ionisation energy ?

Answer 4

Atomic radius (distance from the nucleus ) 
Nuclear charge 
Shielding

Question 5

How does atomic radius affect ionisation energy ?

Answer 5

The greater the distance (atomic radius) the less the attraction between the nucleus and outer electron

Question 6

How does nuclear charge affect ionisation energy ?

Answer 6

The more protons the nucleus has the higher the nuclear charge the higher the attraction between the nucleus and outer electron

Question 7

How does shielding affect ionisation energy ?

Answer 7

The greater the shielding (the more energy levels there are) the weaker the attraction between the nucleus and outer electron

Question 8

What is the trend on a group 2 graph ? (4 bullet points)

Answer 8

• As you go down the group there are more energy levels
• therefore there is more shielding and a greater distance between the nucleus and outer electron
• therefore less attraction between the nucleus and outer electron
• and therefore a lower ionisation energy

Question 9

What is the general trend across period 3 ? (4 bullet points)

Answer 9

• all electrons are in the 3rd shell so shielding is constant
• the nucleus is becoming more positive (due to more protons)
• so the attraction between the nucleus and the outer electron is getting stronger
• therefore the size of the atom decreases as the shells are being pulled closer as you have more protons but the same number of shells

Question 10

Describe the group 2-3 dip across period 3 ( 4 bullet point)

(Can be applied to period 2)

Answer 10

• Mg’s outer electron is in the 3s energy level
• Al’s outer electron is in the 3p energy level
• 3p is more shielded and further from the nucleus
• therefore there is a dip in ionisation energy

Question 11

Describe the group 5 -6 dip in period 3 (3 bullet point)

Answer 11

• phosphorus is 3p3 and sulfur is 3p4.
• pair of electrons In sulfurs 3p sun shell causes a small amount of repulsion
• making the outer electron slightly easier to remove