Ionisation Energy

Question 1

Ionisation is…

Answer 1

Removal of one or more electrons

Question 2

First ionisation energy

Answer 2

Energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 3

First ionisation of oxygen

Answer 3

O(g) ——> O+ (g) + e-

Question 4

3 factors affecting ionisation energy

Answer 4

Nuclear charge

Distance from nucleus

Shielding

Question 5

Nuclear charge

Answer 5

More proteins there are in the nucleus, the more positively charged nucleus is

Stronger the attraction for electrons

Higher ionisation energy

Question 6

Distance from nucleus

Answer 6

Attraction decreases with distance

Electron closer to nucleus will be much more strongly attracted than one further away

Question 7

Shielding

Answer 7

As number of electrons between outer electrons and nucleus increases

Outer electrons feel less attraction to nuclear charge

Lessens pull of nucleus by inner shells of electrons

Question 8

Second ionisation energy

Answer 8

Energy needed to remove one electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

Question 9

2nd ionisation energy equation

Answer 9

O+ (g) ———> O2+ (g) + e-

Question 10

Successive ionisation energy equation using n

Answer 10

(n-1)+. n+. -

X. (g) ————> X (g) + e

Question 11

Within each shell, successive ionisation energies …

Answer 11

Increase

Question 12

Why do successive ionisation energies increase

Answer 12

Electrons are being removed from Increasingly positive ion

Less repulsion amongst remaining electrons

———> held more strongly to nucleus

Question 13

How do successive ionisation energy graphs tell you group in periodic table an element belongs to?

Answer 13

How many electrons are removed before first big jump

Eg 3 are removed until jumps significantly higher in ionisation so element belongs to group 3

Question 14

Electronic structure prediction using graphs

Answer 14

Go from right to left

Count how many point before big jump

Gives oh how many electrons are in each shell starting with first

Question 15

3 trends in ionisation energy

Answer 15

1. 1st ionisation energy down a group decreases
2. 1st ionisation across period generally increases
3. Ionisation energy changes down group 2 + across period 3

Question 16

Ionisation energy ____ across a period

Answer 16

Increases

Question 17

Why does ionisation energy increase across period?

Answer 17

Number of protons increases

Stronger nuclear attraction

Question 18

Ionisation energy _____ down group 2

Answer 18

Decreases

Question 19

The drop in ionisation energy between group 2 and 3 shows _____

Answer 19

Sub shell structure

Question 20

Drop between group 5 and 6 is due to ____

Answer 20

Electron repulsion

Question 21

Electron repulsion

Answer 21

Orbitals hold 2 electrons

If only one electron is in an orbital rather than 2 which are paired

Harder to remove one alone than one in a pair

Question 22

Ionisation energy decreases down group 2, why?

Answer 22

Each element down group 2 has extra electron shell compared to one above

Extra inner shells will shield outer electrons from attraction of nucleus

Extra shell increases distance from nucleus

Decreasing ionisation energy