Question

The number of electrons present in all the completely filled subshells having n=4 and s=+½​ is _____. (Where n = principal quantum number and s = spin quantum number).

Answer 1

Correct Answer: 16

To determine the number of electrons present in all the completely filled subshells with principal quantum number n=4 and spin quantum number s=+½, we first identify the available subshells for n=4. These are 4s, 4p, 4d, and 4f.

Each subshell can hold a specific number of electrons: 

• 4s: 2 electrons
• 4p: 6 electrons
• 4d: 10 electrons
• 4f: 14 electrons

Next, since we are only interested in electrons with s=+½, we consider half of those in each subshell:

Subshell	Total Electrons	Electrons with s=+½
4s	2	1
4p	6	3
4d	10	5
4f	14	7

Summing these, the total number of electrons with s=+½ is 1+3+5+7=16.

This value fits the expected range of 16,16, confirming its correctness. Therefore, the number of electrons in all completely filled subshells with n=4 and s=+½ is 16.

Answer 2

For n = 4, the possible subshells and their electron capacities are:

So, the total number of electrons is 16.