Module 3 Chapter 1 Lesson 2 - Ionisation Energy

Question 1

What is the definition of first ionisation energy?

Answer 1

The energy required to remove 1 mol of electrons from 1 mol of gaseous atoms.

Question 2

What is the definition of second ionisation energy?

Answer 2

The energy required to remove 1 mol of electrons from 1 mol of gaseous ions.

Question 3

What are the three factors affecting ionisation energy?

Answer 3

Atomic Radius (Size of atom)

Nuclear Charge

Shielding

Question 4

What is shielding?

Answer 4

Repulsion between inner and outer shells.

So more shells means more shielding.

Question 5

What is atomic radius?

Answer 5

The size of the atom.

Question 6

What happens to the ionisation energy as you go down a group?

Answer 6

Decreases

Question 7

Why does ionisation energy decrease down a group?

Answer 7

Increased shells
Increased shielding

Increased nuclear charge
Increased atomic radius

Shells and shielding outweigh nuclear charge and atomic radius.

Decreased nuclear attraction between nucleus and outer most electrons.

Decreased ionisation energy.

Question 8

What happens to ionisation energy as you go across a period?

Answer 8

Increases

Question 9

Why does ionisation energy increase as you go across a period?

Answer 9

More protons

Increased nuclear charge

Decreased atomic radius

Increased charge density

Increased nuclear attraction.

Increased ionisation energy.

Distance and shielding stay the same.

Question 10

What happens in terms of ionisation energy between the last element of a period and the first element of the next period?

Answer 10

Decreases

Question 11

Why does ionisation energy decrease between the last element of a period and the first element of the next period?

Answer 11

Increased distance
Increased shells
Increased shielding

Increased nuclear charge
Increased atomic radius

Shells and shielding outweigh increase in nuclear charge and atomic radius.

Question 12

What happens to the ionisation energies of successive elements?

Answer 12

Increases

Question 13

Why is nitrogen a larger atom than oxygen?

Answer 13

N has less protons.

Weaker nuclear attraction in N.

Similar shielding.

Shells drawn in less by nuclear charge in N.

Question 14

Why is the second ionisation energy larger than the first?

Answer 14

First electron is removed from a neutral atom but second is removed from a positive atom.

Stronger nuclear attraction from outer electrons to nucleus.

More energy required/

Question 15

Why is the first ionisation energy of B smaller than Be even though B is after Be in the periodic table?

Answer 15

B - Outer electron removed from 2p orbital.

Be - Outer electron removed from 2s orbital.

The 2p orbital is higher in energy.

2p is more shielded than the 2s orbital.

So outer electron of B is held less strongly.

So lower ionisation energy.

Question 16

Predict and explain whether a sodium ion is larger/smaller/the same size as a sodium atom.

Answer 16

Smaller
Shell is lost
Higher nuclear charge

Question 17

What causes the general decrease of atomic radii/size across each period?

Answer 17

Nuclear charge increases.

Similar shielding

Nuclear attraction increases so pulls in outer shells closer.

Question 18

Why do group 2 elements become more reactive as you go down a group?

Answer 18

Shells increase

Shielding increases

Weaker nuclear attraction

Smaller ionisation energy

So easier to lose electrons

Question 19

Why is the first and second ionisation energies of Sr less than Ca?

Answer 19

Sr has more shells.

So a higher atomic radius

So less attraction

Due to more distance and increased shielding.