7.2 Ionisation energies

Question 1

what is the first ionisation energy?

Answer 1

the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 2

what factors affect ionisation energy?

Answer 2

atomic radius
nuclear charge
electron shielding

Question 3

how does atomic radius affect ionisation energy?

Answer 3

the larger the radius, the weaker the nuclear attraction between the nucleus and outer electrons

more easier to remove an electron

Question 4

how does nuclear charge affect ionisation energy?

Answer 4

the greater the nuclear charge, the more protons

more protons means stronger nuclear attraction
AS the nucleus is more positively charged

Question 5

how does electron shielding affect ionisation energy?

Answer 5

the greater the shielding, the greater the repulsion of outer electrons

weaker nuclear attraction between nucleus and outer electrons

Question 6

why are successive ionisation energies greater?

Answer 6

the next electron to be removed is closer and more attracted to the nucleus so has a stronger nuclear attraction
therefore more energy is required to remove the electron

Question 7

what is the jump in ionisation energy between successive electrons in different shells?

Answer 7

a large difference as the next shell is far more closer to the nucleus so has a stronger attraction

Question 8

outline the trend in ionisation energy DOWN A GROUP

Answer 8

atomic radius increases

electron shielding increases

causes a weaker nuclear attraction between outer electrons and nucleus

less energy needed to remove an electron

Question 9

outline trend in ionisation energy ACROSS A PERIOD

Answer 9

atomic number increases so number of protons increases

shielding stays the same

stronger nuclear attraction as nucleus is more positively charged

atomic radius decreases

more energy is needed to remove an electron

Question 10

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

Answer 10

boron removes an electron from the 2p sub shell

beryllium removes an electron from the 2s sub shell

the 2p sub shell is at a higher energy level and thus further from the nucleus so it is easier to remove the electron

Question 11

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

Answer 11

the outermost electron in oxygen is paired

this electron is repelled by it’s paired electron (electron repulsion)

therefore it is easier to remove this electron

the outermost electron in nitrogen is single so there is no repulsion