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Question: Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize the sodium atom. What is...

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize the sodium atom. What is the ionization energy of sodium per atom?

A

494.5×10−6494.5 \times 10^{- 6} J/atom

B

8169.5×10−108169.5 \times 10^{- 10}J/atom

C

5.85×10−155.85 \times 10^{- 15} J/atom

D

8.214×10−198.214 \times 10^{- 19} J/atom

Answer

8.214×10−198.214 \times 10^{- 19} J/atom

Explanation

Solution

: λ=242nm=242×10−9m\lambda = 242nm = 242 \times 10^{- 9}m

Energy required to ionize one atom of Na (E) = hcλ\frac{hc}{\lambda}

=(6.626×10−34Js)×(3×108ms−1)242×10−9m= \frac{(6.626 \times 10^{- 34}Js) \times (3 \times 10^{8}ms^{- 1})}{242 \times 10^{- 9}m}

=8.214×1019= 8.214 \times 10^{19} J/atom