How many unpaired electrons are contained in each element (a) chlorine (b) selenium (c) cesium and (d) phosphorus?

(a) Chlorine (Cl) has 1 unpaired electron in its outermost shell.
(b) Selenium (Se) has 2 unpaired electrons in its outermost shell.
(c) Cesium (Cs) has 1 unpaired electron in its outermost shell.
(d) Phosphorus (P) has 3 unpaired electrons in its outermost shell.