Which group of elements in the periodic table releases the most energy when gaining an electron (i.e., has the highest electron affinity)?

• A. Group 18 (noble gases)
• B. Group 17 (halogens)
• C. Group 2 (alkaline earth metals)
• D. Group 1 (alkali metals)

Answer: (B)

Verified step by step guidance

1. Understand that electron affinity refers to the amount of energy released when an atom gains an electron to form an anion.
2. Recall that elements with high electron affinity release more energy upon gaining an electron, indicating a strong tendency to accept electrons.
3. Consider the general trends in the periodic table: electron affinity tends to increase across a period from left to right and decrease down a group.
4. Recognize that Group 17 elements (halogens) have high electron affinities because they are one electron short of a full valence shell, making them highly eager to gain an electron and release energy.
5. Note that Group 18 elements (noble gases) have full valence shells and generally do not gain electrons easily, so their electron affinity is low or even positive (energy required), while Groups 1 and 2 have lower electron affinities because they tend to lose electrons rather than gain them.