Question
Can Phosphorus with outer electronic configuration 3s23p3 form PH5?
Or
P forms PH3 but not PH5. Comment.
Solution
Although phosphorus exhibits +3 and +5 oxidation states, yet it can not form PH5. Because of high ∆H–H and slightly negative ∆ e.g. H (electron gain enthalpy), dihydrogen acts only as a weak oxidising agent. Thus it can oxidise P to +3 oxidation state but not to its highest oxidation state of +5. Hence P forms PH3 and not PH5.
