JEE Main · 2019 · 12 Apr 2019 · Shift 2 · Atomic Structure

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Among the following, the energy of 2s orbital is lowest in:
  1. (A)K✓ Correct
  2. (B)Na
  3. (C)H
  4. (D)Li

Answer: (A)

Solution

Orbital energy drops as the effective nuclear charge rises, because the electron is held more tightly. Among , , and , potassium has the largest nuclear charge, so its electrons feel the strongest pull and the orbital lies lowest, most negative, in potassium.

JEE Main · 2019 · 12 Apr 2019 · Shift 2 · Single correct option

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