■ Elements
► | Can combine to form compounds. | |
► | Noble gases, sulphur, gold, silver and diamond exist in their free states. | |
► | Other elements exist as compounds. |
► | A compound is a substance formed when two or more chemical elements are chemically bonded together in fixed ratios. | |
► | Most minerals (compound) on the earth's crust are metallic oxides and sulphides. | |
► | The tendency of elements to combine with other elements show that compounds are more stable than their constituent elements. |
► | All noble gases are very stable, inert and inactive chemically. | |
► | The noble gases do not donate, receive or share any more electrons, as their valence shells are full. |
► | All other elements combine chemically with other elements to attain the stability of the noble gases. | |||||
► | Two types of chemical bonds in compounds are :
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