atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
carbon: The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
electric charge: The physical property responsible for electric force; it can be negative or positive.
electron: A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids. element: A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.
hadron: One of a group of particles that are made up of other, smaller particles — quarks — held together by a particular kind of force. The protons and neutrons found in the nucleus of atoms are hadrons.
hydrogen: The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.
matter: Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."
mean: One of several measures of the “average size” of a data set. Most commonly used is the arithmetic mean, obtained by adding the data and dividing by the number of data points.
neutron: A subatomic particle carrying no electric charge that is one of the basic pieces of matter. Neutrons belong to the family of particles known as hadrons.
particle: A minute amount of something. physicist: A scientist who studies the nature and properties of matter and energy. proton: A subatomic particle that is one of the basic building blocks of the atoms that make up matter. Protons belong to the family of particles known as hadrons.
quarks: A family of subatomic particles that each carries a fractional electric charge. Quarks are building blocks of particles called hadrons. Quarks come in types, or “flavors,” known as: up, down, strange, charm, top and bottom.
subatomic: Anything smaller than an atom, which is the smallest bit of matter that has all the properties of whatever chemical element it is (like hydrogen, iron or calcium).