Which of the following best describes the trends in electronegativity across a period and down a group in the periodic table?

• A. Electronegativity increases across a period and decreases down a group.
• B. Electronegativity decreases across a period and increases down a group.
• C. Electronegativity remains constant across a period and increases down a group.
• D. Electronegativity decreases both across a period and down a group.

Answer: (A)

Verified step by step guidance

1. Understand that electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond.
2. Recall the periodic trends: across a period (left to right), the number of protons in the nucleus increases, which generally increases the effective nuclear charge felt by electrons.
3. Because of the increased effective nuclear charge across a period, atoms more strongly attract electrons, so electronegativity increases from left to right.
4. Down a group (top to bottom), atoms have more electron shells, which increases the distance between the nucleus and the valence electrons and adds shielding effect.
5. This increased distance and shielding reduce the nucleus's pull on bonding electrons, so electronegativity decreases as you move down a group.