Photons travel through space at the speed of light. When the changes of energy are small, streams of photons can be described as waves of changing electric and magnetic fields, called electromagnetic waves. The most familiar type of electromagnetic radiation is visible light, but the full spectrum of electromagnetic radiation includes radio, microwave, infrared, ultraviolet, X rays and gamma rays. The entire range of electromagnetic waves, named in order of increasing frequency or energy, ranges from radio waves, to microwave, to infrared, to visible or optical, to ultraviolet, to X rays, to gamma rays. The union of electricity and magnetism, which do not exist as independent quantities, but are in reality two aspects of a single physical phenomenon.
Electrons orbit the nucleus of an atom.
They can be torn away from an atom by collisions with other particles or photons. The pressure produced by the resistance of electrons to compression once they are squeezed to the point where quantum effects become important. The energy gained by an electron accelerated by a potential of 1 volt. The number of protons in the nucleus of the atom determines which element it represents. The most familiar of the elementary particles are the proton, neutron, and electron.