2.2.5 Structures of Ionic Compounds

Question 1

What is happening in ionic bonding between ions, electrons and in terms of structure?

Answer 1

• Electron transfer
• Each ion is surrounded by oppositely charged ions in all directions
• A giant ionic lattice is made

Question 2

What state are ionic compounds at room temperature and why?

Answer 2

Solid:

1. They have strong electrostatic bonds holding =/- ions together
2. All these forces have to be overcome when melting an ionic substance
3. So they have high melt/boil pts

Question 3

Why is the melting point of Na-Cl+ much higher than Mg2+O2-? How does this impact the usage of MgO?

Answer 3

1. The greater the charge, the stronger the electrostatic attraction between ions
2. So more en needed to break
   - So MgO is used to line furnaces for brick making

Question 4

What is the electrical conductivity like in an ionic substance?

Answer 4

In a solid ionic lattice:
1. Ions no move as positions fixed 
2. So doesn't conduct el
When dissolved in H2O:
1. Fixed structure breaks so ions free move
2. Conducts electricity

Question 5

Why do ionic substances dissolved in polar substances conduct el?

Answer 5

The ions are able to move and carry the charge.

Question 6

Why does an ionic lattice dissolve in polar substances?

Answer 6

1. Define polar: slight charges, as electrons not shared equally
2. The slight charges surround the ionic lattice and attract its charged ions
3. So the lattice is disrupted and ions are pulled out of it

Question 7

Why does Na-Cl+ dissolve in water? How would you draw this?

Answer 7

1. Water molecules surround the ions
2. Na+ attracts delta - charges of the O atom (of H2O)
3. Cl- attracts delta + charges of the H atom (of H2O)
   To draw: Na+ is surrounded by 6 delta - O’s, which are connected to H’s
   Cl is surrounded by four H’s (delta +), two dashy, two wedged