Electronic configuration of an atom is defined as the representation of the position of electrons in the various energy shell & subshells.

Now A negative charge on the species indicates the gain of an electron by it & A positive charge denotes the loss of an electron

(i) (a) H^– ion

The electronic configuration of H atom is 1s¹.(atomic number = 1)

∴ Electronic configuration of H^– = 1s²

(b) Na⁺ ion

The electronic configuration of Na atom is 1s² 2s² 2p⁶ 3s¹.(atomic number = 11)

∴ Electronic configuration of Na⁺ = 1s² 2s² 2p⁶ 3s⁰  Or  1s² 2s² 2p⁶

(c) O^2– ion

The electronic configuration of 0 atom is 1s² 2s² 2p⁴.(atomic number = 8)

∴ Electronic configuration of O^2– ion = 1s² 2s² p⁶

(d) F^– ion

The electronic configuration of F atom is 1s² 2s² 2p⁵.(atomic number = 9)

∴ Electron configuration of F^– ion = 1s² 2s² 2p⁶

(ii) (a) 3s¹

Completing the electron configuration of the element as 1s² 2s² 2p⁶ 3s¹.

∴ Number of electrons present in the atom of the element

= 2 + 2 + 6 + 1 = 11

∴ Atomic number of the element = 11(sodium)

(b) 2p³

Completing the electron configuration of the element as 1s² 2s² 2p³.

∴ Number of electrons present in the atom of the element = 2 + 2 + 3 = 7

∴ Atomic number of the element = 7(nitrogen)

(c) 3p⁵

Completing the electron configuration of the element as 1s² 2s² 2p⁵.

∴ Number of electrons present in the atom of the element = 2 + 2 + 5 = 9

∴ Atomic number of the element = 9(fluorine)

(iii) (a) [He] 2s1

The electronic configuration of the element is [He] 2s¹ = 1s² 2s¹.

∴ Atomic number of the element = 3 (lithium , a p-block element)

(b) [Ne] 3s² 3p³

The electronic configuration of the element is [Ne] 3s² 3p³= 1s² 2s² 2p⁶ 3s² 3p³.

∴ Atomic number of the element = 15(phosphorous, a p block element)

(c) [Ar] 4s² 3d¹

The electronic configuration of the element is [Ar] 4s^₂ 3d¹= 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹.

∴ Atomic number of the element = 21(scandium , a d block element)