# What happens when we heat an atom?

Question is simple.. If we take an atom of any element and then supply heat energy to it then what will happen?

What I thought is that in the beginning, energy (quanta; due to excitement of electron and then moving back to ground state) should be evolved and then electron should be emitted... Am I right?

If we take an atom of any element and then supply heat energy to it then what will happen?

A single atom can move in three dimensions (x, y, z) through space, it cannot rotate about an external axis like a diatomic molecule can, nor can it vibrate. As you supply heat (or any form of energy) to the system containing the atom, it's kinetic energy will increase and it will move faster through space. If you supply enough energy, then the electrons surrounding the atom will absorb that energy and undergo electronic transitions from the ground state to various excited states. This process can be diagrammed using a Morse potential diagram , I've drawn a simple one below. The diagram is meant to show promotion of an electron from the ground electronic state to higher and higher electronic levels as more energy is applied to the system. Note that as the electron is promoted to higher energy levels, the average separation distance between it and the nucleus increases. If enough energy is supplied, an electron will dissociate from the atom and we will be left with an ion. Continue to supply even more energy and more electrons will be removed from the atom. Pumping even more energy into the system will ultimately lead to transformations in the nucleus of the atom.

• Are you sure that the use of a Morse potential diagram is permissible for the description of ionization? Jul 21 '14 at 21:08
• What is your concern, the shape of the left wall? I was trying to use the x-axis to represent some time of 10-90 percentile of the electron's radial distribution function. I thought if I made the left wall vertical or tilted to the right it would raise questions. But to answer your question, I think that the Morse concept can be applied to electron dissociation just like bond dissociation.
– ron
Jul 21 '14 at 21:26
• I've just never seen it being used in this context. I thought it would be only valid for the vibrations of diatomic molecules. Jul 21 '14 at 21:29
• I've seen it used in spectroscopy books and courses to diagram electronic transitions in a molecule.
– ron
Jul 21 '14 at 21:33
• @Philipp I agree, a Morse potential is weird for ionization. The Morse potential picture only comes if you have well defined position for both the nucleus and the electron. It's fine for diatomics in the Born-Oppenheimer picture (classical nuclei), but if you have quantum nuclei or quantum electrons... well, their position is not well defined! Energy diagrams for a particle in a Coulomb potential (with a continuum limit being ionization) would be more fitting. Aug 4 '14 at 21:25

Well, strictly speaking, you can not heat an individual atom, because heat is a macroscopic phenomenon: it is a mechanism of energy transfer from one macroscopic body to another one. And the same is true for the related notion of temperature. But, both temperature and heat can be explained at microscopic level as follows.

Particles that constitute bulk matter are in constant random motion and temperature is nothing but a measure of the mean kinetic energy of particles random motion. Heat then can be understood as macroscopic manifestation of transfers of this kinetic energy of random motion from a statistically significant number of particles of one body to particles of another body.

Thus, you can heat a body (not an individual atom), i.e. you can transfer energy to it by means of heat, and while the body is heated, the mean kinetic energy of all particles (atoms, nuclei, electrons) will rise, i.e. it temperature will rise. The kinetic energy of an electron acquired then can be partly redistributed with its potential energy when electron jumps'' into higher orbital. After excitation the atom may return to the ground state or a lower excited state, by emitting a photon with a characteristic energy.

And, of course, in principle, we could add so much energy to a body be heating, that electrons will indeed leave atoms.