NCERT Class XI Chemistry Structure of Atom Solutions

Question : 16

Total: 67

(i) The energy associated with the first orbit in the hydrogen atom is –2.18 × 10–18Jatom–1. What is the energy associated with the fifth orbit?
(ii) Calculate the radius of Bohr’s fifth orbit for hydrogen atom.

Solution:

(i) Energy associated with nth orbit in hydrogen atom is
En =

−2.18×10−18

Jatom−1
∴ Energy associated with 5th orbit is
E5 =

−2.18×10−18

= - 8.72 × 10−20Jatom−1
(ii) Radius of Bohr’s fifth orbit for hydrogen atom, rn = 0.529 n2 Å
r5 = 0.529 × 52 Å
r5 = 13.225 Å = 13.225 × 10–10 m [Since 1 Å = 10–10 m]
= 1.3225 × 10–9 m = 1.3225 nm [Since 1 nm = 10–9 m]

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