Metals 


Metals are the elements which can form positive ions by losing electrons. For example, Na is a metal because it can form positive ion (Na+) ion by losing an electron from its outermost shell. In the same way Iron, aluminium, copper, gold, silver, magnesium, potassium and calcium are also metals because all of these elements can form positive ions by losing electrons.
It should be noted that the oxides of metals are basic in nature. All metals are solid at room temperature except mercury which is liquid metal.

Almost all metals react with oxygen to form metal oxides. But different metals react with oxygen at different intensities. For example, sodium metal is always kept immersed in kerosene oil. Because, if we keep it open, it reacts so vigorously with oxygen present in air that it catches fire. We have already discussed that the oxides of metals are basic in nature. As all the metals have different reactivity so they combine with oxygen at different temp. 

On heating, magnesium metal burns in air giving magnesium oxide.