Question

Identify the wrong statement in the following.

• A. Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius
• B. Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius
• C. Atomic radius of the elements increases as one moves down the first group of the periodic table
• D. Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the periodic table

Answer 1

The Correct Option is A

To solve this problem, we need to evaluate each statement regarding periodic trends and properties of isoelectronic species.

1. Statement 1: "Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius"
   - Explanation: Isoelectronic species have the same number of electrons. However, their nuclear charges (protons in the nucleus) differ. For cations, a smaller positive charge usually means fewer protons to pull the electron cloud close to the nucleus, which should imply a larger, not smaller, ionic radius. Hence, this statement is incorrect.
2. Statement 2: "Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius"
   - Explanation: As we add negative charge to an isoelectronic series, i.e. adding electrons, repulsion between electrons increases spreading them out, making the ionic radius larger. This statement is correct.
3. Statement 3: "Atomic radius of the elements increases as one moves down the first group of the periodic table"
   - Explanation: Moving down a group adds a new electron shell, increasing the distance between the outermost electrons and the nucleus, thereby increasing the atomic radius. This statement is correct.
4. Statement 4: "Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the periodic table"
   - Explanation: As you move across from left to right in a period, electrons are added to the same shell but nuclear charge increases, pulling electrons closer to the nucleus and decreasing the atomic radius. This statement is correct.

Conclusively, the wrong statement is the first one: "Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius".