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Ionic bonding
Ionic bonding is between ions. One is a metal ion which has lost an electron / electrons, the other is a non-metal ion that has gained an electron / electrons.
Ionic bonding is the transfer of electron(s) to form ions which are held together by electrostatic interaction.
Method
1. Work out how many electrons need to be gained or lost in order to get a full outer shell
2. Work out the charge that the ion will form
3. Draw one type of ion with crosses and draw the other with dots (don’t forget the square brackets and charges)
Sodium Chloride example:
What is happening?
Sodium atom needs to lose 1 electron to give it a full outer shell. This will form a sodium ion with a charge of +1.
Chlorine atom has 7 electrons in its outer shell so need to gain 1 to form a chloride ion. This ion will have a charge of -1
In the reaction between sodium and chlorine one electron is transferred from sodium to chorine to form a sodium ion and a chlorine ion.
These ions have opposite charges (positive and negative) and so the ions are held together via electrostatic attraction
Giant Ionic Substances
Giant ionic substances are made up of millions and millions of ions all held together by electrostatic attraction.
What’s an ion? An atom with a charge (positive or negative) due to the loss or gain of electrons.
What’s electrostatic attraction? The attraction between a positively charged ion and a negatively charged ion
These ions all come together to form a giant ionic lattice. Shown below on the left
Solid
Molten
Boiling and melting point
To melt or boil a giant ionic substance you have to pull apart the ions and therefore, break the electrostatic attractions.
Electrostatic attraction is very strong and so giant ionic substances have high boiling points and melting points.
Electrical conductivity
When the ions are held in place (the substance is a solid, shown above) the ions cannot move and so it cannot conduct electricity. If a giant ionic substance is molten (melted) then the ions are free to move and so it can conduct electricity.
Giant ionic substances dissolve in water. If we dissolve a giant ionic substance in water the ions all move apart and spread out in the water. This means they can move and giant ionic substances can conduct electricity when dissolved.
Examples include sodium chloride (table salt) and any other ionic compound. All ionic compounds form giant ionic substances. Always contains metals and non metals.
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