WRITING FORMULAE [SIMPLE IONIC]

=Ionic Formulae= ===Simple Ionic Compounds=== [image:http://i.imgur.com/3gzvKlN.png] Oppositely charged ions are attracted to each other and bond together to form '''Ionic Compounds'''. When writing ionic formula the metal (positive ion) always goes first. The charges (positive / negative) within an ionic compound must also be balanced. For instance Calcium forms a 2^+^ ion and Chlorine forms a 1^-^ ion. The compound that is formed, Calcium Chloride, will consist of one Calcium ion and two Chloride ions ===[image:http://i.imgur.com/nFhrKox.png]=== Example 2: When sodium (which forms a 1^+^ ion) combines with sulphur (which forms a 2^-^ ion) we will need twice as many sodium ion as sulphur ions. ===[image:http://i.imgur.com/WA1BzdS.png]=== Example 3: When aluminium (forms a 3^+^ ion) combines with sulphur (forms a 2^-^ ion) we will need TWO aluminium ions for every THREE sulphur ions. ==Ionic Formulae== ===Polyatomic Ions=== Polyatomic ions are ions that consist of a small group of atoms that are sharing electrons. This small group can collectively lose or gain electrons to form a charged particle. Some common polyatomic ions are: [image:http://i.imgur.com/VDlNPRh.png] === ===When writing formulae, these ions can be treated in much the same way as simple ions. [image:http://i.imgur.com/9KmfjjA.png] === ===When dealing with polyatomic ions, if you need to use more than one you will need to place it in brackets. For instance When writing the formula for Calcium Nitrate... We will need two Nitrate ions for every Calcium ion because Calcium forms a 2^+^ ion and Nitrate only form a 1^-^ ion [image:http://i.imgur.com/UQH0Jy2.png]