Cuprous ion (Cu+) can not be considered as a transition element while cupric ion '(Cu)^(2+)' is a transition metal ion. Why?

Explanation

Electronic configuration of .(Cu)-1 (~s)^(2) 2 (~s)^(2) 2 (p)^(6) 3 (~s)^(2) 3 (p)^(6) 4 (~s)^(t) 3 (~d)^(10).
.(Cu)^(*)-1 (~s)^(2) 2 (~s)^(2) 2 (p)^(6) 3 (~s)^(2) 3 (p)^(6) 3 (~d)^(t) 0)., completely filled .(d).
orbital.
.(Cu)^(2+)-1 (~s)^(2) 2 (~s)^(2) 2 (p)^(6) 3 (~s)^(2) 3 (p)^(6) 3 (~d)^(9)., partially filled d orbital.
Hence .(Cu)^(2+). is a transition element,