Answer
(a) and (d); (b) and (e); (c) and (f)
Work Step by Step
(a) and (d) both have 5 electrons in p orbitals, meaning that they will align in the same group and have similar chemical properties
(b) and (e) both have only one electron in an s subshell, meaning that they both belong in the alkali metal group
(c) and (f) have all complete subshells, meaning that they both are noble gases and very unreactive
