Question

Which of the following is the correct unit of angular momentum of an lectron in an orbital of an atom?

• A. J -s
• B. J/s
• C. $W/s^2$
• D. W-s

Answer 1

Answer: (A)

J -s

Answer 2

Angular momentum of an electron in an orbital of an atom $(L)=m v r$

To find out the units,

$L=m v \times r= kg \times m s^{-1} \times m$
$L= kg\, m^{2} s^{-1}\,...(i)$

We know that, 1 Joule $= kgm ^{2} s^{-2}$

Multiplying and dividing E (i) by $s^{-1}$
$L = kg\, m^{2} s^{-1} \times \frac{s^{-1}}{s^{-1}}$
$= kg m^{2} \frac{s^{-2}}{s^{-1}}$
$L = J - s$

Hence, the unit for angular momentum of an electron in an orbital is $J - s$.