Question

The number of electrons in an atom that may have the quantum numbers n=3 and m=+1/2 is

• A. 9
• B. 32
• C. 18
• D. 16
• E. 8

Answer 1

The Correct Option is A

We are given the principal quantum number n = 3 and spin quantum number m_s = +1/2.

For n = 3, the possible values of the azimuthal quantum number l are:

• l = 0 (s-subshell)
• l = 1 (p-subshell)
• l = 2 (d-subshell)

Each subshell has the following number of orbitals:

• s: 1 orbital
• p: 3 orbitals
• d: 5 orbitals

Total orbitals for n = 3: 1 + 3 + 5 = 9

Each orbital can hold 2 electrons, one with spin +1/2 and one with spin -1/2.

So, the number of electrons with m_s = +1/2 will be:

9 orbitals × 1 electron per orbital = 9 electrons

Correct Answer:

Correct Answer: (A) 9