# What's the thermal energy of a helium atom?

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1. Jan 9, 2016

### JoAstro

I have this formula "E= 1/2 mv^2" which I don't fully understand. Also, I don't have the values for helium's mass and velocity.

2. Jan 9, 2016

### Andrew Mason

Welcome to PF JoAstro!

It is not clear what your question is. Individual atoms do not have a temperature. But large numbers of atoms can have a temperature. Is the question you are trying to answer: what is the average kinetic energy of a helium atom in a volume of helium gas that is at a particular temperature?

The kinetic energy of a body of mass m moving at speed v is $KE = \frac{1}{2}mv^2$. And the average kinetic energy of the atoms of a monatomic gas at a temperature T is: $<KE> = \frac{3}{2}kT$

AM

3. Jan 10, 2016

### JoAstro

Hi Andrew. Thank you!!

I'm not sure about what you say, but I just noticed that I misread the question thinking it was another. The real question was meant for hydrogen which said "What is the typical thermal energy of a hydrogen atom?" However, the question I meant to ask was "What is the velocity of a helium atom in the photosphere of a star?"