ionisation energy

Question 1

first ionisation energy

Answer 1

the energy required to remove one mole of gaseous electrons from one mole of gaseous atoms to provide one mole of gaseous 1+ ions

Question 2

first ionization energy formula

Answer 2

X(g)→X + (g)+e −

Question 3

why are they gaseous?

Answer 3

easiest state to be ionized

Question 4

units of ionization energy

Answer 4

kilojoules per mole (kj mol-1)

Question 5

factors affecting ionization energy

Answer 5

-size of nuclear charge
- distance of outer shell electrons from nucleus
-shielding of inner electrons
-spin pair repulsion

Question 6

what is the trend of IE energy across a period, and down a group

Answer 6

across the period= increase in IE
down a group= decrease in IE

Question 7

what are the deviations across a period

Answer 7

Mg to Al drops
P to S drops

Question 8

explain why the IE increases across a period

Answer 8

-the no of protons increase across the period, so higher nuclear charge
- the nucleus will become more positive
- the atomic radius decreases, as there is a stronger nuclear attraction between the nucleus and outer shell electrons, as they will be drawn inwards tightly
-shielding is not affected as they have the same no of energy levels

Question 9

explain why the IE decreases going down the group

Answer 9

-There is a larger atomic radius, as there is an increase in energy levels due to having more electrons
-this means that there is a larger distance between the nucleus and outer shell electrons, so there is a weaker nucleur attraction between them
- shielding also affects it, as there are more electrons, in which the innershtell electrons repel the outer shell electrons

Question 10

explain why the second ionisation energy is greater than the first

Answer 10

• the atom is becoming more positive, as there are more protons than electrons after the first IE
• the electron is being removed from a positive species, requiring more energy
• this means that there is a stronger nuclear attraction

Question 11

why does the first IE drop from P to S?

Answer 11

• P will have 3 unpaired electrons in the 3p orbital
• S will have paired electron in one orbital, in which the electrons will experience repulsion
• So P will have a higher IE energy as its more stable