Question

Which element from following is NOT regarded as transition element ?

• A. \(\text{Cu}\)
• B. \(\text{Sc}\)
• C. \(\text{Cd}\)
• D. \(\text{Au}\)

Hint:

A transition element has an incomplete d subshell in the atom or in its common ions; Cd has a full d10 in both.

Answer 1

The Correct Option is C

Step 1: Understand the concept
A transition element has a partly filled d subshell either in the atom or in at least one of its common oxidation states.

Step 2: Check Cu, Au and Sc
Cu (\(3d^{10}4s^1\)) forms \(\text{Cu}^{2+}\) with \(3d^9\). Au forms \(\text{Au}^{3+}\) with \(5d^8\). Sc has \(3d^1 4s^2\) in the atom. Each has an incomplete d subshell in the atom or an ion, so each is regarded as a transition element.

Step 3: Check Cd
Cd has \(4d^{10}5s^2\) and its only common ion \(\text{Cd}^{2+}\) is \(4d^{10}\). The d subshell is full in both the atom and the ion.

Step 4: Conclusion
Cd is the element not regarded as a transition element.

Final Answer:
Cd has a completely filled d subshell in atom and ion. This is option (C). \[ \boxed{\text{(C) }\text{Cd}} \]