3.1.2 Ionisation energy

Question 1

what is first ionisation energy?

Answer 1

the energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions

Question 2

when does ionisation occur?

Answer 2

when atoms lose of gain electrons
-become an ion

Question 3

what state is first ionisation energy always calculated in?

Answer 3

gaseous

Question 4

how does first ionisation increase and decease?

Answer 4

INCREASES ACROSS A PERIOD
decreases down a group

Question 5

what does ionisation energies show?

Answer 5

periodicity

Question 6

how do elements form a positive ion?

Answer 6

energy must be supplied to an electron to overcome their attraction to the positive nucleus
(negative electrons are held in their shells by their attraction to the positive nucleus)

Question 7

which electrons are removed first?

Answer 7

electrons in the outer shell

Question 8

why are electrons removed from the outer shell first?

Answer 8

because they experience the least amount of nuclear attraction (they are the furthest away from the nucleus and tf require the least ionisation energy)

Question 9

what does the nuclear attraction experienced by an electron depend on?

Answer 9

-atomic radius
-nuclear charge
-electron sheilding

Question 10

the larger the atomic radius, …

Answer 10

the smaller the nuclear attraction is

Question 11

why is the nuclear attraction smaller, the larger the atomic radius is?

Answer 11

the positive charge of the nucleus is further away from the outermost electrons

Question 12

the higher the nuclear charge, …

Answer 12

the higher the nuclear charge, the larger the attractive forces between the nucleus and outer electrons (so more energy is required to overcome these attractive forces when removing an electron)

Question 13

what is electron shielding?

Answer 13

when the inner shells of electrons repel the outer shell electrons because they are all negative

Question 14

what is the effect of more inner shells on electron shielding?

Answer 14

the more inner shells there are, the larger the electron shielding effect and the smaller the nuclear attraction experience by the outer electrons

Question 16

what are successive ionisation energies?

Answer 16

a measure of the amount of energy required to moved each electron in turn

Question 17

how many ionisation energies do elements have?

Answer 17

an element has as many ionisation energies as it has electrons

Question 18

lithium has three electrons
how many successive ionisation energies?

Answer 18

3

Question 19

does the ionisation energy decrease or increase across a period?

Answer 19

increase

Question 20

why does the ionisation energy increase across a period?

Answer 20

nuclear charge increases across a period, there is no significant change in atomic radius, therefore no shielding is experienced

Question 21

when can a rapid change in ionisation energy be observed?

Answer 21

there is a rapid decrease in ionisation energy between the last element in a period and the first element of the next element

Question 22

why is there a rapid change in ionisation energy between the last element in a period and the first element of the next period?

Answer 22

there is an increased distance between the nucleus and the outermost electrons (atomic radius) therefore there is more electron shielding (this outweighs the increased nuclear charge)

Question 23

what are two examples of exceptions to the rule about ionisation energies across a period?

Answer 23

there is a slight decrease in ionisation energy between beryllium and boron, and nitrogen and oxygen

Question 24

how does the ionisation. energy between beryllium and boron stray from the expected?

Answer 24

there is a slight decrease in ionisation energy

Question 25

why is there a slight decrease in ionisation energy between beryllium and boron?

Answer 25

as the 5th electron in boron is in the 2p sub shell which is further away from the nucleus than the 2s subshell of beryllium

Question 26

how does the ionisation energy between nitrogen and oxygen stray from expected?

Answer 26

there is a slight decrease in ionisation energy

Question 27

why is there a slight decrease in ionisation energy between nitrogen and oxygen?

Answer 27

as the paired electrons in the 2p sub shell of oxygen repel each other, making It easier to remove an electron from oxygen rather than nitrogen

Question 28

what is the trend in first ionisation energy down a group?

Answer 28

nuclear charge increases whilst ionisation energy DECREASES?

Question 29

why do does ionisation energy decrease down the group?

Answer 29

-nuclear charge increases
-atomic radi increases
-more electron shielding
-attraction between nucleus and outermost electrons decrease
-easier to remove electrons

Question 30

what happens to the successive ionisation energies of an element as electrons are removed?

Answer 30

it increases as removing an electron from a positive ion is harder than a neutral atom

Question 31

why is it increasingly harder to remove electrons?

Answer 31

as more electrons are removed, the attractive forces increase, due to decreasing shielding and an increased proton to electron ratio

Question 32

what is the increase in successive ionisation energy dependent on?

Answer 32

electron configuration

Question 33

describe the overall trend in successive ionisation energy

Answer 33

it is not constant and it dependant on each elements electron configuration

Question 34

how do you interpret successive ionisation energy graphs?

Answer 34

read right to left, first shell to outermost
-the graph shows which electrons are removed first

Question 35

what do the big jumps in a successive ionisation energy graph show?

Answer 35

change of shell

Question 36

what do the small jumps in a successive ionisation energy graph show?

Answer 36

change of sub shell