5.2 Ionic bonding

Question 1

define an

Ionic Bond

Answer 1

electrostatic attraction between positive and negative ions.

Question 2

How are ionic bonds formed?

Answer 2

By atoms losing or gaining electrons

More electronegative non-metal atoms GAIN electronsFROM metal atoms

Question 3

Ions are isoelectronic with nearest noble gas

Answer 3

two atoms,ions or molecules that have the same electronic structure and same number of valence electrons.

Question 4

ANIONS

Answer 4

(-) are formed
when atoms (USUALLY
NON-METALS) gain
electrons from metal

Question 5

CATIONS

Answer 5

(+) are formed
when atoms (USUALLY
METALS) lose electrons
to non-metal

Question 6

Group 4 :

Answer 6

Group 4 :

🡺No 4+ ions : too much energy to remove 4 e-

🡺 No 4- ions: too much repulsion between 4 added e-

🡺 some 2+ ions: lower in group eg Sn2+ and Pb2+

Question 7

define

ion

Answer 7

An ion is just a charged particle. Whereby atoms have either lost or gained electrons.

Question 8

Dot and cross diagrams

Answer 8

Drawing full diagrams from the first shell to their current valence shell (valence refers to the
outer shell, or shell/electrons used in bonding), takes a lot of time and effort.

At A-level, only outer shells are needed.

Question 9

describe the structure of

ionic compounds

Answer 9

On a small scale we have looked at the lowest common ratio of ions needed to form a
particular ionic compound.

However, salts form bonds in all directions. This results in the formation of a giant ionic
lattice – containing millions upon billions of ions in a repeating pattern.

Question 10

GIANT IONIC LATTICE

Answer 10

Oppositely charged ions held in a regular

3-dimensional lattice by electrostatic attraction

The arrangement of ions in a crystal lattice depends on the relative sizes of the ions

Question 11

list the three

Properties of ionic compounds

Answer 11

• Melting and boiling points
• Solubility
• Electrical Conductivity

Question 12

explain

Melting and boiling points in ionic compounds

Answer 12

• The bonds between ions are very strong, and at low temperatures there is insufficient energy
  to overcome these electrostatic forces of attraction.
• Higher temperatures provide greater amounts of energy to overcome these electrostatic
  forces of attraction.
• Ionic lattices with greater ionic charges have higher melting points due to a stronger
  attraction between ions.

e.g. melting points

• NaF: 993oC, where as CaF2: 1423oC

-Na2O: 1275oC where as CaO: 2614oC

Question 13

explain

Electrical conductivity of ionic compounds in dif states

Answer 13

Electrical conductivity – SOLID:
In a solid state, ionic compounds do NOT conduct electricity.
The ions are held too strongly in the fixed position of the giant ionic lattice, and therefore
can not move and carry the charge.

Electrical conductivity – AQUEOUS or MOLTEN
When the ionic compound is dissolved in water, or melted, it DOES conduct electricity.
The solid ionic lattice breaks down, allowing the ions to move freely. They are now mobile
and can carry the charge.

Question 14

explain s

solubility of ionic compounds

Answer 14

• Many ionic compounds require a polar solvent to dissolve. E.g. water
• Polar water molecules have the ability to break down the ionic lattice and then surround
  each ion in each solution.
• If the forces of attraction are too strong, the ability of the ionic lattice to be broken down
  is reduced rendering the compound sparingly soluble.
• For ionic compounds, the solubility decreases as the ionic charge increases
  (or the electrostatic forces of attraction get stronger)

solubility requires two main
processes:

• The ionic lattice must be broken down
• Water molecules must attract and surrounded the ions

Question 15

Physical properties of ionic compounds

Strength

Answer 15

Very brittle. Any dislocation leads to the layers moving and similar ions being adjacent.
The repulsion splits the crystal.