15 - Periodicity

Question 1

Define ionisation energy

Answer 1

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

Question 2

What is the first ionisation energy?

Answer 2

The energy to take off the first electron (making a 1+ iron from an atom)

Question 3

What are the 3 factors which affect ionisation energy?

Answer 3

Charge of nucleus

Distance from nucleus

Electron shielding

Question 4

What is electron shielding?

Answer 4

The repulsion between electrons in inner shells

Question 5

What is the overall factor which affects ionisation energy?

Answer 5

Attraction

Attraction is affected by ionisation energy, charge of nucleus and electron shielding.

Question 6

What is the relationship between overall attraction and ionisation energy?

Answer 6

As attraction increases

Ionisation energy also increases

Question 7

What is the relationship between charge of nucleus and attraction?

Answer 7

As the charge of the nucleus increases, attraction increases

Question 8

What is the relationship between attraction and electron shielding?

Answer 8

As the electron shielding increases, attraction increases

Question 9

What happens to the 3 factors which affect ionisation energy as you go down a group?

Answer 9

Distance from nucleus increases

Charge of nucleus increases

Shielding increases

They all increase

Question 10

What happens to ionisation energy (and attraction) as you go down a group?

Answer 10

As you go down a group, ionisation energy decreases

Question 11

What happens to ionisation energy (and attraction) as you go across the groups from left to right?

Answer 11

Ionisation energy increases

Question 12

What are the 2 exceptions to the fact that ionisation energy increases as you go across a period?

Answer 12

Ionisation energy decreases across a period when:

A new orbital is added (from 1s^2 2s^2 to 1s^2 2s^2 2p^1 for example)

Which happens from group 2 to 3

Or the outermost electron of an element is spin paired when the element to the left doesn’t have the outermost electron in a spin pair (outer electron in O is spin paired by not N do O has a lower IE than N despite O being to right of N)

Which happens from group 5 to 6

Question 13

Why does having a spin paired outer electron decrease ionisation energy?

Answer 13

This electron is repelled by the other electron in the spin pair so it is much easier to remove

Question 14

What are successive ionisation energies?

Answer 14

Measure of energy required to remove each electron in turn from each atom of 1 mole of substance

Like second, third ionisation energy

Question 15

What is the chemical equation showing lithium being ionised?

Answer 15

Li(g) –> Li(g)+ + e-

The gas state symbols are very important

Question 16

What happens to the value of ionisation energy when you go from first, to second ionisation energy and so on?

Answer 16

As order of ionisation energy increases, ionisation energy increases too

First IE < Second IE < Third IE and so on

Question 17

What happens to ionisation energy when an outer shell is lost due to electrons being lost by ionisation?

Answer 17

The ionisation energy suddenly increases when an outer shell is lost

Question 18

What happens to electron shielding as you go across a period and why?

Answer 18

It doesn’t change

Because you are filling up the same shell

Question 19

Describe precisely what happens to boiling point as you go across the groups

Answer 19

From group 1 to 14, there is a general increase in boiling point

From group 14 to 15, there is a sharp increase in boiling point

From group 15 to 18, the boiling point is very low

Question 20

Explain why silicon has a much higher boiling point than phosphorus

Answer 20

Silicon has strong covalent bonds but phosphorus only has London forces

Question 21

Explain why boiling point increases from sodium to aluminium

Answer 21

Aluminium has ions with greater charge so the metallic bonds are stronger in aluminium

Question 22

What is electron shielding proportional to?

Answer 22

The number of shells