Question

Which of the following statement is incorrect about the periodic trend?

• A. Atomic radii decrease while going from left to right in a period and increase with atomic number in a group.
• B. Ionisation enthalpies generally decrease across a period and increase down a group.
• C. Electronegativity generally increases across a period and decreases down a group.
• D. Electron gain enthalpies in general, become more negative across a period and less negative down a group.
• E. Among representative elements, the valence is equal to the number of electrons in the outermost orbital.

Hint:

Chemistry Tip: Stronger nuclear attraction across a period makes electron removal harder, so ionization enthalpy rises.

Answer 1

The Correct Option is B

Concept:
Periodic properties follow predictable trends across periods and down groups.
Step 1: Check statement (A).
Correct. Radius decreases across period and increases down group.
Step 2: Check statement (B).
Actual trend of ionization enthalpy is: - Increases across a period - Decreases down a group But statement says opposite. Hence incorrect.
Step 3: Check others briefly.
(C) Correct general trend.
(D) Correct general trend.
(E) Correct for representative elements in simplified sense.
Therefore incorrect statement is Option (B). :contentReference[oaicite:1]{index=1}