NCERT Class XI Chemistry Structure of Atom Solutions

Question : 19

Total: 67

The electron energy in hydrogen atom is given by En = (–2.18×10–18)∕n2J. Calculate the energy required to remove an electron completely from the n = 2 orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

Solution:

En =

−2.18×10−18

J
E2 =

−2.18×10−18

(2)2

−2.18×10−18

= - 0.545 × 10−18 = - 5.45 × 10−19J
Wavelength of light (λ) =

6.626×10−34×3×108

5.45×10−19

= 3.647 × 10−7m
= 3647 × 10–10 m = 3647 Å [Since Å = 10–10 m]

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