There are just over 110 elements that make up all matter in our universe. Ninety-two are naturally occurring (92 is Uranium). That above Uranium is man-made with short half-lives. All elements have unique properties. Pure elements such as gold are rare in the natural world.
Most matter is a combination of elements such as methane (the gas we use to heat our houses) which is made of carbon and hydrogen. Atoms are the smallest unit of an element that conserves the properties of that element. Each atom comprises three types of particles, neutrons, protons, and electrons. Protons have a positive charge; electrons are negatively charged. Neutrons are not charged. The atom’s nucleus contains protons and neutrons; the electrons move about in orbits around the nucleus.
The electrons are kept in orbit around the nucleus by the attraction between the positively charged protons and the negatively charged electrons.
The proton number establishes which element it is. For example, an aluminum atom has 13 protons in the nucleus, and a copper atom has 29. The number of electrons in an atom equals the number of protons, and the atom is electrically neutral. This means no net charge.
It would be impossible to depict all the orbits in a drawing, so an oversimplified version using concentric circles around the nucleus is used. Each circle on the diagram symbolizes an energy level. The outermost electrons are called valence electrons; the inner electrons are designated core electrons.
Valence electrons are the furthest from the nucleus of all electrons in an atom. Since they are farther away, their attraction to the positively charged nucleus is the least of all the electrons in an atom. An atom can lose or gain one or more valence electrons, resulting in a net charge. An entity with a net charge is called an ion.
Electricity is the flow of electrons from one atom to another from an area with an excess negative charge to a more positively charged site. The ability of an atom to lose its valence electrons leads directly to the phenomenon of electricity. If an electron moves from one atom to another, the gaining species is negatively charged and known as an anion. The losing atom is now positively charged and is known as a cation. In the big scheme of things charge is conserved, but these new entities are now players in electron flow.
Several methods, including an electrochemical reaction or the application of friction, light, pressure, or a moving magnetic field, can produce these areas of surplus electron charge. The moving magnetic field, used in electromagnetic induction, began with Faraday’s discovery of induction. He showed how a changing magnetic field could induce an electric current. In this way, mechanical energy is transformed to electric energy.
Valence electrons also participate in chemical bonding. When two atoms share valence electrons, they form bonds and become molecules. A molecule is several atoms bonded together with no electrical charge. It is the smallest unit of a compound that retains the characteristics of that compound. So while the molecule is electrically neutral and does not play a part in electricity, ionic compounds have a charge. When dissolved in a solvent can facilitate electron flow, also called current.