L7: Ionic Bonding

Question 1

What is the octet rule?

Answer 1

Most atoms show a tendency to adjust their valence shells to 8 e- by losing, gaining, or sharing electrons

Question 2

What is the most notable exception to the octet rule?

Answer 2

Transition metals using d-orbitals obey the 18 electron rule instead

Question 3

What is the most electronegative element?

Answer 3

Fluorine - small, high nuclear charge

Question 4

True or false: Electronegativity increases across a period, and decreases down a group

Answer 4

True

Question 5

True or false: Ionic bonding involves the sharing of electrons between atoms

Answer 5

False. In ionic bonding one or more electron is fully transferred between atoms

Question 6

True or false: Ionic bonding takes place between metals and non-metals

Answer 6

True

Question 7

True or false: Forming an ionic bond involves a decrease in energy compared to the two isolated atoms

Answer 7

True

Question 8

True or false: Ionic bonds are directional

Answer 8

False

Question 9

True or false: Ionic compounds disassociate in polar solvents, such as water

Answer 9

True

Question 10

True or false: Ionic compounds have an overall charge

Answer 10

False. Ionic compounds are neutral

Question 11

True or false: Ionic bonds are broken when the compound is melted

Answer 11

True

Question 12

True or false: Ionic compounds form crystalline solids with low melting temperatures

Answer 12

False. They form crystalline solids with HIGH melting temperatures

Question 13

True or false: Ionic compounds conduct electricity when molten and/or in solution

Answer 13

True

Question 14

What is ‘lattice energy’?

Answer 14

The enthalpy of forming one mole of the ionic solid from its gaseous ions

Question 15

True or false: Ionic compounds form giant lattice structures

Answer 15

True

Question 16

In order to favour ionic bond formation, what electronegativity difference is needed between the cation and the anion?

Answer 16

The larger the better

Question 17

True or false: To form an anion, a metal should have a low ionisation energy

Answer 17

False. Metals don’t form the anion, they form the cation. And for cation formation, a low ionisation energy is favourable.

Question 18

True or false: To form an anion, a non-metal should have a high electron affinity

Answer 18

True

Question 19

When is an ionic compound likely to have some covalent character?

Answer 19

When (a) the cation is small and/or has a high charge; or, (b) the anion is large and/or has a high charge

Question 20

How do ionic compounds gain some covalent character?

Answer 20

By polarisation - instead of being spherical, the anion loses it’s shape and is pulled towards the cation

Question 21

What are the five important cations in the body?

Answer 21

1) Sodium
2) Potassium
3) Calcium
4) Hydrogen
5) Magnesium

Question 22

What are the five important anions in the body?

Answer 22

1) Chloride
2) Bicarbonate
3) Hydrogenphosphate
4) Sulphate
5) Phosphate