They, in turn, emit low-energy infrared light, some of which is prevented from escaping the atmosphere by greenhouse gases. All of these processes, reflection, absorption and reflection of infrared from the Earth involve the atomic changes that have been described above. If we observe light emitted from the fixtures in the lecture hall we see that they contain many different colors, or energy levels. If we, instead, observe light produced by electrons changing levels in helium gas we observe only a few distinct colors of light. Affinities of atoms and the periodic table.
Different atoms have different numbers of electrons, protons and neutrons.
The number of protons in an atom gives its atomic number . Atoms of some elements, such as helium or argon, have completely filled outer shells. The periodic table of the elements shows atomic numbers and how shells are filled with electrons for all the elements. Consequently, it is easy for those atoms to give up that one electron. For example, NaCl, the molecule with a sodium and a chlorine atom, is otherwise known as table salt.