Verified Solution • 2025–26 Session moderate

QPage 383: Q5: HC Verma: Concepts of Physics - Volume 2 Bohr's Model and Physics of the Atom Page 383: Q5 Solution: In which of the following systems will the radius of the first…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often use $r_n = a_0 n^2/Z$ without the reduced‑mass factor, assuming all hydrogen‑like systems have the same $\mu\approx m_e$. In reality $r_n = a_0 n^2/(Z\,\mu/m_e)$, so isotopes (H vs D) and light ions differ slightly; forgetting this leads to an incorrect ranking of radii.

In which of the following systems will the radius of the first orbit n=1n = 1) be minimum?

Multiple Choice Options

  • A Hydrogen atom
  • B Deuterium atom
  • C Singly ionized helium
  • D Doubly ionized lithium

Step-by-Step Verified Solution

**Answer:** (d) Doubly ionized lithium. **Step-by-Step Explanation:** r_n = a_n_/Z. For n=1, the smallest radius is for the largest Z, which is Li__ (Z=3).

All Questions in this Chapter

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