Atoms have a tendency to complete their outer energy level. this is known as
decomposition
synthesis
the octet rule
the rule of electrons

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).

the answer is d.) potassium

it is b that is the answer.