In general, the property (magnitudes only) that shows an opposite trend in comparison to other properties across a…

🧠 Across a period: $IE$, electronegativity, and $|\Delta_{eg}H|$ all rise. Atomic radius is the only one that falls The three "attraction-related" properties (IE, EN, EGE magnitude) all measure how strongly an atom holds or pulls electrons. Across a period, $Z_{eff}$ rises, so all three magnitudes rise together. Atomic radius measures the SIZE — and as the same-shell electrons are pulled closer by more protons, the atom shrinks.

🗺️ Compare directions across a period Ionization enthalpy: increases (electrons harder to remove). Electronegativity: increases (atom pulls bonded electrons harder). Electron gain enthalpy magnitude: increases (becomes more negative, so $|\Delta_{eg}H|$ rises). Atomic radius: decreases — opposite direction.

The question asks which property's magnitude moves opposite to the others. Atomic radius.

⚠️ The trap Some students pick (c) electron gain enthalpy because they remember "$\Delta_{eg}H$ becomes more negative" and confuse "more negative" with "decreasing". The question says "magnitudes only" — so we are comparing $|EGE|$, which rises across a period like the other attraction properties. Only atomic radius shrinks.

$\boxed{\text{Answer: (d)}}$