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Question:

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

Solution:

(a) P with atomic number 15 with electronic configuration [Ne]3s²3p³ contains 3 unpaired electrons.
(b) Si with atomic number 14 with electronic configuration [Ne]3s²3p² contains 2 unpaired electrons.
(c) Cr with atomic number 24 with electronic configuration [Ar]3d⁵4s¹ contains 6 unpaired electrons.
(d) Fe with atomic number 26 with electronic configuration [Ar]3d⁶4s² contains 4 unpaired electrons.
(e) Kr with atomic number 36 [Ar]3d¹⁰4s²4p⁶ contains 0 unpaired electrons.