Assertion A: Energy of 2s orbital of hydrogen atom is greater than that of 2s orbital of lithium. Reason R: Energies of…
Structure of Atom · Class 11 · JEE Main Previous Year Question
Assertion A: Energy of 2s orbital of hydrogen atom is greater than that of 2s orbital of lithium. Reason R: Energies of the orbitals in the same subshell decrease with increase in the atomic number.
Choose the correct answer:
- a✓
Both A and R are true and R is the correct explanation of A.
- b
Both A and R are true but R is NOT the correct explanation of A.
- c
A is true but R is false.
- d
A is false but R is true.
Both A and R are true and R is the correct explanation of A.
🧠 The Nuclear Grip Energy of an electron is like a debt. The more protons () pulling on an orbital, the "deeper" the debt (lower/more negative the energy).
🗺️ The Atomic Audit
- Assertion A: TRUE. Lithium () has a much stronger positive nucleus than Hydrogen (). It pulls its 2s electrons much closer, making their energy more negative (lower). Thus, the energy of H(2s) is "higher" (less negative) than Li(2s).
- Reason R: TRUE. As increases, the electrostatic attraction becomes stronger, pulling all orbitals to lower energy levels.
Since the stronger pull of is exactly why the lithium well is deeper, Reason R is the correct explanation.
⚡ The "Sun-Gravity" Analogy A planet around a massive star (Lithium) is held in a tighter, deeper orbit than a planet around a small star (Hydrogen).
⚠️ Common Traps Don't confuse "greater energy" with "greater stability." Stability is low energy. Hydrogen's 2s is "higher" on the energy chart (closer to zero).
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