The electron configuration of an atom is a representation of the arrangement of electrons in its atomic orbitals. The orbitals are grouped into energy levels or shells, and each level can hold a specific number of electrons. The first shell can hold a maximum of two electrons, the second can hold up to eight electrons, the third can hold up to 18, and so on.

In the given atom, the electron configuration can be represented as:

- 2 electrons in the first shell (K shell)
- 8 electrons in the second shell (L shell)
- 8 electrons in the third shell (M shell)
- 2 electrons in the fourth shell (N shell)

This represents a total of 20 electrons in the atom.



The values of m and s represent the orientation and spin of the electron, respectively. The value of m can range from -l to +l, where l is the orbital angular momentum quantum number. For s orbitals, l=0, so m can only be 0. The value of s can be either +1/2 or -1/2, depending on the direction of the electron's spin.

Therefore, the electrons with m=0 and s=1/2 are those that are in the s orbitals of the atom. In this case, there are two s orbitals in the first shell, and two s orbitals in the fourth shell. Each s orbital can hold a maximum of two electrons, so the total number of electrons with m=0 and s=1/2 is:

- 2 electrons in the first shell
- 2 electrons in the fourth shell

This represents a total of 4 electrons.



Therefore, the correct answer is (b) 2.

Total electron= 2+8+8+2=20 .
electronic configuration=1S2 2S2 2P6 3S2 3P6 4S2.
total 4 s-orbital having 4 electron (m=0 s=1/2) and 2 p-orbital having 2 electron (m=0 s=1/2) .
4+2= 6 electron .
option A is correct.