What are the atomic numbers of elements whose outermost electrons are represented by

(a) 3s¹ (b) 2p³ and (c) 3p⁵?

[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]