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

Question

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. What is the ionisation energy of sodium per atom? (A) 494.5 × 10-6 J/atom (B) 8169.5 × 10-10 J/atom (C) 5.85 × 10-15 J/atom (D) 8.214 × 10-19 J/atom

Tardigrade Admin · Accepted Answer

λ=242 nm =242×10-9 m Energy required to ionise one atom of Na, E=(hc/λ) =((6.626 × 10-34 J s) × (3 × 108 m s-1)/242 × 10-9 m) =8.214 × 10-19 J /atom

Q. Electromagnetic radiation of wavelength $242 nm$ is just sufficient to ionise the sodium atom. What is the ionisation energy of sodium per atom?

$494.5 \times 1 0^{- 6} J / a t o m$

$8169.5 \times 1 0^{- 10} J / a t o m$

$5.85 \times 1 0^{- 15} J / a t o m$

$8.214 \times 1 0^{- 19} J / a t o m$

$λ = 242 nm$
$= 242 \times 1 0^{- 9} m$
Energy required to ionise one atom of $N a$ , $E = \frac{h c}{λ}$
$= \frac{( 6.626 \times 1 0 ^{- 34} J s ) \times ( 3 \times 1 0 ^{8} m s ^{- 1} )}{242 \times 1 0 ^{- 9} m}$
$= 8.214 \times 1 0^{- 19} J / a t o m$

Q. Electromagnetic radiation of wavelength 242nm is just sufficient to ionise the sodium atom. What is the ionisation energy of sodium per atom?

494.5×10−6J/atom

8169.5×10−10J/atom

5.85×10−15J/atom

8.214×10−19J/atom