Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

Identify the incorrect statement among the following:

Amongst isoelectronic species, the smaller the positive charge on the cation, the smaller is the ionic radius

Amongst isoelectronic species, the greater the negative charge on the anion, the larger is ionic radius

Atomic radius of the elements increases as one moves down the first group of the periodic table

Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the periodic table

Analyze Isoelectronic Species: These are species with the same number of electrons. Their ionic radii depend on the effective nuclear charge ( $Z_{eff}$ ). The radius is inversely proportional to the nuclear charge (number of protons).
Evaluate Option A: For cations with the same number of electrons (e.g., $Na^+$ and $Mg^{2+}$ ), the one with the smaller positive charge ( $Na^+$ , Z=11) has fewer protons attracting the electrons compared to the one with the higher charge ( $Mg^{2+}$ , Z=12). Fewer protons mean less attraction and a larger radius. Therefore, the statement that 'smaller positive charge... smaller radius' is incorrect.
Evaluate Option B: Greater negative charge implies fewer protons for the same number of electrons, leading to less attraction and a larger radius. This statement is correct.
Evaluate Option C: Moving down a group adds new electron shells, increasing the atomic radius. This is correct.
Evaluate Option D: Moving left to right across a period increases the nuclear charge without adding shells, pulling electrons closer and decreasing the radius. This is correct.

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