Chapter 7 Ionisation Energies

Question 1

Ionisation energy

Answer 1

Measure of how easily an atom loses electrons to form positive ions

Question 2

1st ionisation energy

Answer 2

The energy required to rem0ove 1 electron from each atom in 1 mole of gaseous atom of an element to form 1 mole of gaseous 1+ ions.

Question 3

Factors affecting ionisation energy

Answer 3

• Atomic radius
• Nuclear charge
• Electron shielding

Question 4

Factors affecting ionisation energy: Atomic radius

Answer 4

The greater the distance between the nucleus and the outer electrons of an atom = less nuclear attraction

Question 5

Factors affecting ionisation energy: Nuclear charge

Answer 5

The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons

Question 6

Factors affecting ionisation energy: Electron shielding

Answer 6

• Shielding effect - reduces attraction between the nucleus and outer electrons

Question 7

Shielding effect

Answer 7

Electrons are negatively charged and so inner-shell electrons repel outer-shell electrons

Question 8

How many ionisation energies does an element have?

Answer 8

As many electrons as the element has

Question 9

2nd ionisation energy

Answer 9

The energy required to remove 1 electron from each ion in 1 mole of gaseous 1+ ions of an element to form 1 mole of gaeous 2+ ions

Question 10

What do successive ionisation energies allow predictions to be made about?

Answer 10

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

Question 11

Trend of ionisation energies down a group?

Answer 11

Decreases

Question 12

Why do ionisation energies decrease down a group?

Answer 12

• Atomic radius increases
• More inner shells so shielding increases
• Nuclear attraction on outer electrons decreases
• first ionisation energy decreases

Question 13

Trend in 1st ionisation energy across a period

Answer 13

Increases

Question 14

Why does 1st ionisation energy increase across a period

Answer 14

• Nuclear charge increases
• Same shell, so similar shielding
• Nuclear attraction increases
• Atomic radius decreases
• 1st ionisation energy increases

Question 15

Metallic bonding

Answer 15

Strong electrostatic attraction between cations and delocalised electrons

• The cations are fixed in position -> maintains the structure and shape of the metal
• The delocalised electrons are mobile and are able to move throughout the structure

Question 16

Solid metal structure

Answer 16

Each atom has donated its negative outer shell electron to a shared pool of electrons which are delocalised throughout the whole structure

Question 17

Delocalised

Answer 17

Spread out

Question 18

Properties of metals

Answer 18

• Strong metallic bonds - attraction between cations and delocalised electrons
• High electrical conductivity
• High melting and boiling points

Question 19

Properties of metals: Electrical conductivity

Answer 19

• Conduct electricity in solid and liquid states
• When a voltage is applied across a metal, the delocalised electrons can move throughout the structure (carrying charge)

Question 20

Properties of metals: Melting and boiling points

Answer 20

High melting and boiling points - high temperatures are required to provide large amount of energy needed to overcome the strong electrostatic attraction between cations and electrons

Question 21

Properties of metals: Solubility

Answer 21

Insoluble

Question 22

Giant covalent lattice

Answer 22

Many billions of atoms held together by a network of strong covalent bonds

Question 23

Giant covalent lattice: Carbon and silicon

Answer 23

• Both have 4 bonds = tetrahedral (109.5 degrees)

Question 24

Properties of giant covalent structures: Melting and boiling points

Answer 24

High melting and boiling points
Strong covalent bonds require high energy to be broken

Question 25

Properties of giant covalent structures: Solubility

Answer 25

Insoluble -> covalent bonds in lattice are too strong to be broken by interaction with solvents

Question 26

Properties of giant covalent structures: Electrical conductivity

Answer 26

Non-conductors of electricity
All electrons are in covalent bonds

Question 27

Special cases of electrical conductivity of giant covalent structures

Answer 27

• Graphene and graphite