Note: If you are interested, you could follow these links to benzene or to organic acids. For the purposes of this topic, you don't need to understand how this bonding has come about. This is a rather more complicated version of the bonding you might have come across in benzene or in ions like ethanoate. Unfortunately, in real carbonate ions all the bonds are identical, and the charges are spread out over the whole ion - although concentrated on the oxygen atoms. This shows two single carbon-oxygen bonds and one double one, with two of the oxygens each carrying a negative charge. If you worked out the structure of a carbonate ion using "dots-and-crosses" or some similar method, you would probably come up with: Its charge density will be lower, and it will cause less distortion to nearby negative ions. It has a high charge density and will have a marked distorting effect on any negative ions which happen to be near it.Ī bigger 2+ ion has the same charge spread over a larger volume of space.
Exactly the same arguments apply to the nitrates.Įxplaining the trend in terms of the polarising ability of the positive ionĪ small 2+ ion has a lot of charge packed into a small volume of space.
#CAESIUM NITRIDE HOW TO#
Note: If you are working towards a UK-based exam (A level or its equivalent) and haven't got copies of your syllabus and past papers follow this link to find out how to get hold of them.ĭetailed explanations are given for the carbonates because the diagrams are easier to draw, and their equations are also easier. You should look at your syllabus, and past exam papers - together with their mark schemes You need to find out which of these your examiners are likely to expect from you so that you don't get involved in more difficult things than you actually need. This page offers two different ways of looking at the problem. The ones lower down have to be heated more strongly than those at the top before they will decompose. The nitrates also become more stable to heat as you go down the Group.īoth carbonates and nitrates become more thermally stable as you go down the Group. Magnesium and calcium nitrates normally have water of crystallisation, and the solid may dissolve in its own water of crystallisation to make a colourless solution before it starts to decompose.Īgain, if "X" represents any one of the elements:Īs you go down the Group, the nitrates also have to be heated more strongly before they will decompose. Brown nitrogen dioxide gas is given off together with oxygen. The nitrates are white solids, and the oxides produced are also white solids. The effect of heat on the Group 2 nitratesĪll the nitrates in this Group undergo thermal decomposition to give the metal oxide, nitrogen dioxide and oxygen. The carbonates become more stable to heat as you go down the Group.
If "X" represents any one of the elements:Īs you go down the Group, the carbonates have to be heated more strongly before they will decompose. Thermal decomposition is the term given to splitting up a compound by heating it.Īll of these carbonates are white solids, and the oxides that are produced are also white solids. The effect of heat on the Group 2 carbonatesĪll the carbonates in this Group undergo thermal decomposition to give the metal oxide and carbon dioxide gas. It describes and explains how the thermal stability of the compounds changes as you go down the Group. This page looks at the effect of heat on the carbonates and nitrates of the Group 2 elements - beryllium, magnesium, calcium, strontium and barium. THERMAL STABILITY OF THE GROUP 2 CARBONATES AND NITRATES Thermal decomposition of the Group 2 carbonates and nitrates
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