Question

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

Answer 1

(a) P with atomic number 15 with electronic configuration $\left[Ne\right]3s^{2}3p^3$ contains 3 unpaired electrons.
(b) Si with atomic number 16 with electronic configuration $\left[Ne\right]3s^{2}3p^2$ contains 2 unpaired electrons.
(c) Cr with atomic number 24with electronic configuration $\left[Ar\right]3d^{5}4s^1$ contains 6 unpaired electrons.
(d) Fe with atomic number 26 with electronic configuration $\left[Ar\right]3d^{6}4s^2$ contains 4 unpaired electrons.
(e) Kr with atomic number36 $\left[Ar\right]3d^{10}4s^{2}4p^6$ contains 0 unpaired electrons.