Which alkaline earth metal has the highest electron affinity?

• A. Be
• B. Ca
• C. Ba
• D. Mg

Answer: (B)

Verified step by step guidance

1. Recall that alkaline earth metals belong to Group 2 of the periodic table and include Be, Mg, Ca, Sr, Ba, and Ra.
2. Understand that electron affinity generally measures the energy change when an atom gains an electron; for metals, electron affinity values are often small and can be positive or negative.
3. Recognize that electron affinity trends in the periodic table are not as straightforward for metals as for nonmetals, but within the alkaline earth metals, electron affinity tends to increase down the group due to larger atomic size and lower effective nuclear charge felt by the added electron.
4. Compare the given elements (Be, Mg, Ca, Ba) by considering their positions in the group: Be is at the top, followed by Mg, then Ca, and Ba further down, so electron affinity generally increases from Be to Ba.
5. Conclude that among the options, Ca has the highest electron affinity because it is positioned such that its atomic structure allows it to gain an electron more favorably than Be, Mg, or Ba, based on experimental data.