A system of physical chemistry - Index of


A system of physical chemistry - Index of


resolved in terms of the three space co-ordinates X, Y, Z. Such a

of freedom '

particle possesses three degrees {cf. Fig. 2, diagram {d)).

The kinetic energy in virtue of this " space " vibration is evidently

fRT, and since any vibration ^ involves an amount of potential energy

equivalent to the kinetic, the total energy of i gram-atom of a monatomic

solid is 3RT, according to the principle of equipartition of energy.

Now the atomic heat Cv at constant volume is simply the change of

total atomic energy per degree, that is—


dT (3RT) = 3R = 5-955 cals.

The application of the. equipartition principle has therefore led to the

conclusion that the atomic heat of monatomic solids s/iould be a constant,

viz. 5 "955, tJie same for all monatomic solids and itidependent of temperature

(the term 3R does not contain T ; though, of course, the

total ettergy present in the solid at any given temperature depends on

this temperature, viz. 3RT in the above case). This result is practi-

cally identical with Dulong and Petit's experimentally discovered law,

and this agreement is one of the most striking pieces of evidence in

favour of the equipartition principle. The following table gives the

values of atomic heats for a number of elements at 20° C. {cf G. N.

l-iO-'fi'is, Journ. Anier. Chem. Soc, 29, 1168, 1907): —

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