Indicate the number of unpaired electrons in: (a) P, (b) Si, (c). Cr, (d) Fe and (e) Kr

Explanation

The electronic configurations and number of unpaired electrons present in them are as follows.
(a) `P (Z=15) , : 1s^2 2s^2 2p^6 3s^2 3p_x^1 3p_y^1 3p_z^1`, No. of unpaired electrons = 3
(b) Si (Z =14) : `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p_(x)^1 3p_(y)^1`, No. of unpaired electrons = 2
(c) Cr (Z=24) , `1s^2 2s^2 2p^6 3s^2 3p^6 3d^(5) 4s^(1)`, No. of unpaired electrons =6 (5 in 3d in 1 in 4s -orbitals)
(d) Fe (Z=26), `1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2`, No. of unpaired electrons =4 (in 3d)
(e) Kr (Z=36), `1s^2 2s^2 2p^6 3s^2 3p^6 3d^(10) 4s^2 4p^6` No. of unpaired electrons =0 (Noble gas, no. of electrons unpaired)