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Chemistry · Periodicity of Elements and Periodic Properties

JEE Main 2025 — 28 January, Morning Shift — Question 26

The incorrect decreasing order of atomic radii is :

  1. Option A:

    Mg>Al>C>O\mathrm{Mg}>\mathrm{Al}>\mathrm{C}>\mathrm{O}

  2. Option B:

    Al>B>N>F\mathrm{Al}>\mathrm{B}>\mathrm{N}>\mathrm{F}

  3. Option C:

    Be>Mg>Al>Si\mathrm{Be}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Si}

    Correct
  4. Option D:

    Si>P>Cl>F\mathrm{Si}>\mathrm{P}>\mathrm{Cl}>\mathrm{F}

Answer: C

Step-by-step solution

Atomic radius increases down a group and decreases across a period.

A is correct because size decreases across period 3 and C > O across period 2.

B is correct because Al is below B and size decreases across period 2.

C is incorrect because Mg is below Be, so Mg > Be. Given order starts with Be > Mg, which is wrong.

D is correct because size decreases across period 3 and Cl > F down the group.

Thus, the correct answer is option C.

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
28 January, Morning Shift
Subject
Chemistry
Chapter
Periodicity of Elements and Periodic Properties
Topic
Periodicity in Physical Properties (shielding and sizes)

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