D Continental drift and b
Elements present in group 18 are known as noble gases. The outermost shell of these elements are completely filled.
18 is the answer
One half-life: 5 grams
Two half-lives: 2.5 grams
...a metal atom will *lose* electrons to form a *positive* cation and a nonmetal atom will *accept* electrons to form an *negative* anion.
Answer:
Oxygen is the most contain in earth but you asked in a,b,c and d. So I'll choice A. aluminium.