Ionic Bonding
The Standard - Sodium Chloride
Some naming info:
· Compounds ending in –ide are simple binary compounds containing 2 elements. Even if there is no metal e.g H2S – hydrogen sulphide
· Ending in –ate means oxygen is present
e.g. CaS = calcium sulphide
CaSO4 = calcium sulphate
· Ending in –ite less oxygen present than in –ate compounds
e.g. NaS = sodium sulphide
NaSO4 = sodium sulphate
NaSO3 = sodium sulphite
Definition : Ionic bonding is the result of electrostatic attraction between two oppositely charged ions. The positive ions are formed from metals (usually) and negative ions are usually formed from non-metals
The standard - Sodium Chloride
E.g. Sodium chloride
So any bonding electrons are pulled firmly onto the Cl atom leaving a positive Na and a negative Cl.
Both now have a noble gas configuration
· They have a full outer ‘shell’
· Isoelectronic with Ne and Ar respectively
NB When elements react, their atoms gain or share electrons to reach a more stable arrangement, which is usually that of a noble gas with a full outer energy level (shell) of electrons. This full outer ‘shell’ contains eight electrons; it is often called the ‘octet’.
Lithium oxide
Electron configuration
Li = 2,1
O = 2,6 So O needs 2 electrons, Li can lose only one!
Or using electron in boxes:
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1s |
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2s |
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1s |
2s |
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2p |
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1s |
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2s |
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The lone 2s electron moves into the vacant 2p orbital and the same happens for the other lithium atom.
Lithium Oxygen Lithium
Because oxygen is more electronegative than lithium, it is able to completely remove the electron from the 2s orbital. Both now have full outer shells. In the case of lithium 1s and oxygen has a full 2p electron.
In terms of electrons in electrons in boxes:
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1s |
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2s |
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1s |
2s |
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2p |
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1s |
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2s |
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¯ |
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Notice the empty 2s orbital and full 2p orbital!
So the formula of Lithium oxide must be Li2O.
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