NCERT Class XI Chemistry Structure of Atom Solutions

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Question : 18
Total: 67
What is the energy in joules, required to shift the electron of the hydrogen atom from the first Bohr orbit to the fifth Bohr orbit and what is the wavelength of the light emitted when the electron returns to the ground state? The ground state electron energy is –2.18 × 1011 ergs.
Solution:  
Energy (E) = 2.18 × 1018 J (
1
ni2
1
nf2
)

where , ni = inital orbit , nf = final orbit
E = 2.18 × 1018(
1
12
1
52
)
= 2.18 × 1018(
1
1
1
25
)
= 2.18 × 1018×
24
25

= 2.09 × 1018 J = 2.09 × 1011 erg [Since 1 J = 107 erg]
Wavelength =
hc
E
=
6.626×1027×3×1010
2.09×1011

= 9.51 × 106 cm = 951 × 108 cm = 951 Å
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