Structure and Bonding

Ionic bonding is the attraction between oppositely charged ions.

Ions are formed when electrons are lost or gained from atoms to form positive or negative ions with noble gas configuration. (Full outer shell)

E.g.     Mg:

Trends in Ionic Size:    

a) Postive ions are much smaller than their respective atom, due to the outer electron is in an engery level closer to nucleus.

b) Negative ions are slightly larger than their respective atoms, due to more electrons than protons. Therefore slightly less atrraction from the nucleus

c) Down a group ionic size increases as outer electron is in an energy level further away from the nucleus.

d) Isoelectronic ions (same electron configuration): The larger the charge, the smaller the ion

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Ionic bond is defined as: strong electrostatic forces of attraction between oppositely charged ions, and hence determines their properties.

The structure is GIANT IONIC LATTICE:

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6:6 Co-ordinate means each Na+ is surronded by 6 Cl- 

Properties:

a) High melting point: Due to electrostatic forces of attraction between oppostiely charged ions.

b) Brittle: When layers of ions slide over each other, similar charges are opposite each other and repulsion occurs.

c) Conductivity:

     -Solids: Doesn't conduct as ions can't move

     -Molten/ Aqueous: Does conduct as IONS ARE FREE TO MOVE

Polarisation:

Ionic compounds will be polarised (distorted) when:

a) The positive ion is small and highly charged

b) The negative ion is LARGE with a small charge

more to come