Question

Helium, carbon, argon which of the following element is unstable?

Answer 1

carbon is unstable because it's outermost shell is not filled and needs 4 electrons to become stable.

Answer 2

Among these elements.carbon is the unstable atom.atoms are said to be stable if they have completely filled electronic configuration.

Carbon have 4 electrons in it outermost shell,and to.be stable elements should have completely filled 8 electrons in its outer most shell,like argon,though helium is an exception.