Periodic Table

To find the correct statement regarding periodic properties, let's analyze each option:

1. Electron Affinity Order is F > O > Cl: This is incorrect. The actual electron affinity order is Cl > F > O. Chlorine has a higher electron affinity than fluorine because fluorine has a smaller atomic size, leading to increased electron-electron repulsion in its compact 2p orbital.
2. First Ionisation Energy Order is Al > Mg > K: This is incorrect. The correct order should be Mg > Al > K. Magnesium has a higher ionization energy than aluminum because Mg has a filled s subshell, making it more stable and requiring more energy to remove an electron. Potassium, being in the next period with a larger atomic size, has a lower ionization energy.
3. Atomic Radius Order is N > P > As: This is incorrect. The appropriate order based on periodic trends is As > P > N. This is because atomic radius increases down a group in the periodic table due to the addition of electron shells.
4. Ionic Radius Order is K⁺ > Ca²⁺ > Mg²⁺: This is correct. Potassium ion (K⁺) has a larger ionic radius than calcium ion (Ca²⁺) and magnesium ion (Mg²⁺). The K⁺ ion has lost its outermost electron and has a larger radius due to its lower charge compared to Ca²⁺ and Mg²⁺. Ca²⁺ and Mg²⁺ have higher positive charges, drawing electrons closer and reducing the ionic size.

Therefore, the correct statement is: Ionic radius order is K⁺ > Ca²⁺ > Mg²⁺.