An element X has the electron configuration [Ar] 3d^5 4s^1. Which of the following statements about element X is correct?
Show the answer and explanation
Correct answer
B. It is a transition metal.
Principle or equation
The periodic table is organized by atomic number, and the electron configuration determines the block and group of an element. Elements with partially filled d orbitals are transition metals (d-block).
Why this answer is correct
The configuration [Ar] 3d^5 4s^1 has a partially filled 3d subshell, which is characteristic of transition metals. Noble gases have filled s and p subshells (except He). Halogens have ns^2 np^5 configurations. Alkali metals have ns^1 configurations but with no d electrons. Therefore, X is a transition metal.
Example
Chromium has the configuration [Ar] 3d^5 4s^1 and is a transition metal.
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