Chemistry
posted by timmy123 .
Did I answer these correctly?
1. What is the total number of principal energy levels or shells in an atom with an atomic number of 30?
a. 3
b. 4
c. 5
d. 6
I choose b.
2. The electron configuration of an atom in the ground state is 24. The total number of occupied principal energy levels in this atom is
a. 1
b. 2
c. 3
d. 4
I choose b.
3. In an atom that has an electron configuration of 27, what is the total number of electrons in its principal energy level of highest energy?
a. 2
b. 5
c. 6
d. 7
I choose a.
21. What is the total number of occupied principal energy levels in an atom of 11Na?
a. 1
b. 2
c. 3
d. 4
I choose c.

1. What is the total number of principal energy levels or shells in an atom with an atomic number of 30?
a. 3
b. 4
c. 5
d. 6
I choose b.
Correct.
2. The electron configuration of an atom in the ground state is 24. The total number of occupied principal energy levels in this atom is
a. 1
b. 2
c. 3
d. 4
I choose b.
I don't know what 24 or 27 means. If it means 2 electrons in n = 1 and 4 in n = 2, then b is correct.
3. In an atom that has an electron configuration of 27, what is the total number of electrons in its principal energy level of highest energy?
a. 2
b. 5
c. 6
d. 7
I choose a.
a is correct if that means 2 electrons in n = 1 and 7 in n = 2.
21. What is the total number of occupied principal energy levels in an atom of 11Na?
a. 1
b. 2
c. 3
d. 4
I choose c.
Correct 
thanks