A metal rail rusting in damp weather.
A neutral carbon doesn't lack any electrons. It has exactly the same number of electrons as it has neutrons.
However, it has four electrons in its outer shell in comparison with eight electrons for a noble gas.
In that sense, it needs four electrons to complete its second shell.<span />
Air is it gas so it fills its container, the balloon, completely.
It tends to in increase because the size of the atoms increase.
