# Physical Chemistry : Principles of Quantum Mechanics

## Example Questions

### Example Question #1 : Principles Of Quantum Mechanics

How many sublevels are there with n = 2 in an atom?

20

16

18

9

12

18

Explanation:

The types of subshells, from smallest to largest, are as follows: s, p, d, and f. These four subshells correspond respectively to the following quantum numbers: 0, 1, 2, and 3. The total number of orbitals in an atom with n = 3 is 32 or 9: one 3s , three 3p and five 3d. Each orbital can hold a maximum of 2 electrons. Therefore, the maximum number of electrons possible is 2 x 9 = 18.

### Example Question #2 : Principles Of Quantum Mechanics

What is the maximum number of electrons possible with n = 4 in an atom?

Explanation:

The types of subshells, from smallest to largest, are as follows: s, p, d, and f. These four subshells correspond respectively to the following quantum numbers: 0, 1, 2, and 3. The total number of orbitals in an atom with n = 4 is 42 or 16: one 4s , three 4p , five 4d and seven 4f. Each orbital can hold a maximum of 2 electrons. Therefore, the maximum number of electrons possible is 32.