Could you help me with two physics questions?

Question

1. Each orbit surrounding an atom is allowed _____.

A) only 2 electrons

B) only 8 electrons

C) an unlimited number of electrons

D) a limited number of electrons

2. Where is most of the mass of an atom located?

A) in the nucleus

B) in the orbits

C) in the electrons

D) it is split between the nucleus and the orbits

I think they are both A, but I don't know.

Answer 1

D and A

the first orbital is limited to 2, the next energy level may contain more than 2 electrons.

Answer 2

1. The answer is D--The first orbit has up to 2, the second up to 8, the third up to 18 ---but the valence orbit never has more than 8 regardless of where is it.

2. A

Answer 3

D, because the first has up to 2, the second has up to 8, the third has up to 8, and whatever on

A

Answer 4

Look, We cant just decide on the no of electrons orbiting an atom. We;d need the atomic number. It follows 2*n^2, where n is the shell (orbit) number. The first orbit takes 2, next takes 8 (only if the atom has that much of atomic number!!). SO, it all depends onatomic number. The Ans for 1 is D. A limited no of atoms.  

For question 2: ans is A. The nucleus. :)

ATB