ionisation

Question 1

define 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

explain factors affecting ionisation energy

Answer 2

nuclear charge (num of protons in the nucleus) greater the charge, the greater the nuclear attraction on outer electrons
- atomic radius(distance of the outermost electron from nucleus) a sthis increases, attraction decreases
-electron sheilding( the repulsionbetween electrons from inner shells and oter shell electron) sheilding effect reduces net nuclear attraction. more inner shells, greater effect, weaker attraction

Question 3

explain the general trend down a group

Answer 3

first ionisation energy decreases down a group because:
- there are more shells so more electron sheilding form inner shell electrons
_ the atomic radius increases
_ the increased electron sheilding and atomic radius, far outweighs the increase in nuclear charge
_ therefore the nuclear attraction on the outer shell electrons decreases
_ so a lower inisation enrgy is needed to remove the outer electron

Question 4

expain the general trend accross a period

Answer 4

the first ionisation energy shows a general increase accross a period because:
- the outer electron fills the same shell so electron sheilding stays the same
_ the number of protons increases so nuclear charge increases
_ atomic radius decreases
- therefore there is a greater nyclear attraction on the outer electrons
- more energy is needed to remove the outer electron

Question 5

What’s evidence for subshells

Answer 5

2p sub shell has higher energy than the 2s sub shell

Question 6

Define successive ionization energies

Answer 6

A measure of the energy required to remove each electron in turn

Question 7

Explain why successive ionization energies always increase with ionization number

Answer 7

Each time an electron is removed, the proton:electron ratio increases
Therefore there is a higher greater nuclear attraction on the remaining electrons

Question 8

What predictions can be made from successive ionisation energies

Answer 8

-the number of electrons in outer shell
-the group of the element in periodic table
-the identity of an element

Question 9

why do successive ionisation energies always increase with ionisation number?

Answer 9

-as electrons are removed, the proton:electron ratio increases
-so same number of protons attracting fewer electrons
-this means as each electron is removed there will be greater nuclear attraction on the outer electron
-so more energy required to remove it

Question 10

explain why first ionisation energy of B is less than Be?

Answer 10

-B outer electron in p subshell
-Be in s sibshell
-2p orbital is higher energy than 2s
-so less energy needed to remove electron from B

Question 11

Explain the decrease in first ionisation energy between group 5 and 6 (e.g. N→O, P→ S)

Answer 11

• In (e.g.) Nitrogen, each p orbital contains 1 electron; in (e.g.) Oxygen, one p orbital contains two paired
  electrons
• Paired electrons repel each other, so less energy is needed to remove the electron from (e.g.) Oxygen