Which of the following electron configurations represents a transition metal atom?

• A. [Ne] 3s^2 3p^5
• B. [Kr] 5s^2 4d^{10} 5p^2
• C. [He] 2s^2 2p^6
• D. [Ar] 3d^5 4s^1

Answer: (D)

Verified step by step guidance

1. Recall that transition metals are elements that have an incomplete d subshell in either their atoms or common ions. Typically, these are elements in the d-block of the periodic table, where the d orbitals are being filled.
2. Analyze each given electron configuration to identify if the d subshell is partially filled, which is characteristic of transition metals.
3. For the configuration [Ne] 3s^2 3p^5, note that it corresponds to a p-block element (specifically chlorine), since the 3d subshell is not occupied.
4. For the configuration [Kr] 5s^2 4d^{10} 5p^2, observe that the 4d subshell is completely filled (10 electrons), and the outermost electrons are in the 5p subshell, indicating a p-block element, not a transition metal.
5. For the configuration [He] 2s^2 2p^6, this corresponds to a noble gas (neon), with no d electrons present, so it is not a transition metal.
6. Finally, for the configuration [Ar] 3d^5 4s^1, the 3d subshell is partially filled (5 electrons), which is a hallmark of transition metals. This confirms that this configuration represents a transition metal atom.