The total internal energy of an object is the sum of the average energy of each of the atoms that make up the object. Hence, at certain temperature , it is possible that some atoms are more energetic than others.(These atoms occupy a high energy level than others)
To find the ratio of number of atoms at a higher energy level Ex to the number of atoms at a lower energy level Eo:
$\frac{N_{x}}{N_{o}} = e^{ – \frac{E_{x} – E_{o}}{kT}}$, where
Nx is the number of atoms with energy Ex
No is the number of atoms with energy Eo
k is the Boltzmann constant: 1.381 x 10-23 J/K
T is the temperature in K
