3.1 Ionic bonding

Question 1

Why do chemical bonds form

Answer 1

. When atoms bond together they share or transfer electrons to achieve a more stable electron arrangement, eg a full outer shell

Question 2

Describe process of ionic bonding

Answer 2

. Occurs between metals and non metals
. Electrons are transferred from metal atoms to non metal atoms
. Positive and negative ions are formed

Electrostatic forces of attraction form between them, keeping them together/bonded

Question 3

Describe process of bonding for sodium chloride

Answer 3

• Sodium is in group 1 so has 1 outer electron, but 11 electrons overall
• Chlorine has 7 outer electrons but 17 electrons overall
• An electron is transferred, so the single outer electron of the sodium atom moves into the outer main level of the chlorine atom

So each main level is full

. Sodium forms a 1+ ion because it has lost a negative electron
. Whilst chlorine forms a 1- ion because it has gained a negative electron

These two ions are attracted to each other and to oppositely charged ions in the sodium chloride by
ELECTROSTATIC FORCES OF ATTRACTION

Question 4

Describe the structure of ionic compounds

Answer 4

. They exist in a structure called a lattice

. Because of the electrostatic attraction between oppositely charged ions

. The attraction extends throughout the compound

. Eg every positive ion attracts every negative ion and vice versa

Question 5

Describe the bonding in magnesium oxide

Answer 5

. Magnesium has two electrons on its outer shell as it is in group 2
. Oxygen has 6 electrons on its outer shell as it is in group 6

So the magnesium gives its electrons to oxygen, so the two electrons go to oxygen giving both a full outer shell.

. This leaves the magnesium ion Mg2+ as it has lost two negative electrons
. And the oxide ion O2- which has gained two negative electrons

The formula is MgO and it exists in a lattice

Question 6

Why do ionically bonded compounds have high melting and boiling points

Answer 6

. They are solids at room temperature and have giant structures.

. This is because the ionic compounds are held together by electrostatic forces of attraction between positive and negative ions so lots of energy must be supplied to break these bonds/the lattice of ions.

Question 7

Do ionically bonded compounds conduct electricity

Answer 7

. They conduct electricity when molten or dissolved in water, but NOT when solid.

. This is because the ions that carry charge are free to move around in liquid state so can carry charge throughout the structure. However in solid state they can’t move around

Question 8

Why are ionic compounds brittle and easily shattered when given a sharp blow

Answer 8

. They form a lattice of alternating positive and negative ions, so a blow in a direction can move some ions so that there is contact between ions with like charges.
This can make the structure shatter

Question 9

Solubility of ionic compounds

Answer 9

. Soluble as they can dissolve in water

. This is because the water molecules are polar (part of the molecule have a small negative charge, and some other parts have a small positive charge)
. This means the water molecules pull the ions away from the lattice and cause it to dissolve.