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Taking the Bohr radius as a0 = 53 pm, the radius of Li++ ion in its ground state, on the basis of Bohr’s model, will be about ______.

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प्रश्न

Taking the Bohr radius as a0 = 53 pm, the radius of Li++ ion in its ground state, on the basis of Bohr’s model, will be about ______.

विकल्प

  • 53 pm

  • 27 pm

  • 18 pm

  • 13 pm

MCQ
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उत्तर

Taking the Bohr radius as a0 = 53 pm, the radius of Li++ ion in its ground state, on the basis of Bohr’s model, will be about 18 pm.

Explanation:

Bohr’s radius of orbit (for Hydrogen and H,-like atoms): For an electron around a stationary nucleus, the electrostatic force of attraction provides the necessary centripetal force.

i.e., `1/(4πε_0) ((Ze)e)/r^2 = (mv^2)/r`  ......(i)

Also `mvr = (nh)/(2pi)`  ......(ii)

From equations (i) and (ii), the radius of nth orbit

`r_n = (n^2h^2)/(4pi^2 kZme^2) = (n^2h^2ε_0)/(pimZe^2) = 0.53 n^2/Z Å`  ......`(k = 1/(4πε_0))`

⇒ `r_n ∝ n^2/Z` or `r_n ∝ 1/Z`

`r_n = a_0 n^2/Z`, where a0 = the Bhor radius = 53 pm

‘The atomic number (Z) of lithium is 3.

As `r_n = a_0 n^2/Z`,

Therefore, the radius of Li++ ion in its ground state, on the basis of Bohr’s model. will be about `1/3` times to that of Bohr's radius.

Therefore, the radius of lithium ion is near r = `53/3` = 18 pm.

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अध्याय 12: Atoms - Exercises [पृष्ठ ७५]

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एनसीईआरटी एक्झांप्लर Physics Exemplar [English] Class 12
अध्याय 12 Atoms
Exercises | Q 12.01 | पृष्ठ ७५

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