d and f Block ElementshardMCQ SINGLE⭐ Must-Do

The atomic radii of Iron (), Cobalt (), and Nickel () in the middle of the 3d series are virtually id and f Block Elements Chemistry Question

Question

The atomic radii of Iron ($Fe$), Cobalt ($Co$), and Nickel ($Ni$) in the middle of the 3d series are virtually identical. What is the fundamental quantum mechanical explanation for this plateau?

Answer: B

💡 Solution & Explanation

Atomic size is a tug-of-war between Effective Nuclear Charge (ENC) pulling inward and interelectronic shielding pushing outward. In the middle of the series, the inward pull of added protons is perfectly neutralized by the outward push of the added $3d$ shielding electrons.

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