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S5-16. The radius of a Bohr orbit is given by the formula below: The symbols o,

ID: 544343 • Letter: S

Question

S5-16. The radius of a Bohr orbit is given by the formula below: The symbols o, h, e, and me denote, respectively, the permittivity of vacuum (Chapter 1), Planck's constant, the magnitude of the electronic charge, and the mass of the electron. Numerical values for all these physical constants are tabulated in Appendix C of Principles of Chemistry. (a) Compute ao. (b) Compute the orbital radius of a hydrogen electron in the first shell. (c) Do the same for a hydrogen electron in the second shell. (d) Once more: for a hydrogen electron in the third shell 5-17. Repeat the preceding exercise for He: Calculate ri,2, and rs, and explain the trend.

Explanation / Answer

17.

a0 = 53.8 pm

Given,

rn =53.8 * n2 / Z

Where, n = number of shell

Z = atomic number

For Helium, Z =2

(i)

r1 = 53.8 * (1)2 / 2 = 26.9 pm

(ii)

r2 = 53.8 * (2)2 / 2 = 107.6 pm

(iii)

r3 = 53.8 * (3)2 / 2 = 242.1 pm

as the n value increases the radius of shell also increases.