Alkali Metal
A Group 1 metal.
Alkaline Earth Metal
A Group 2 metal.
Anion
A negative ion.
Atom
The fundamental unit of which elements are composed.
Atomic Number
The number of protons in the nucleus of an atom..
Cation
A positive ion.
Chemical Formula
A representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present and subscripts are used to show the relative number of atoms. For example, water is H2O
Chemical Property
The ability of a substance to change to a different substance.
Dalton's Atomic Theory
John Dalton's theory that all matter is made up of atoms.
Diatomic Molecule
A molecule composed of two atoms.
Electron
A negatively charged particle that occupies the space around the nucleus of an atom.
Element
A substance that cannot be decomposed into simpler substances by chemical or physical means. It consists of atoms all having the same atomic number.
Element Symbol
Abbreviations for the chemical elements.
Group (periodic table)
A vertical column of elements.
Ion
An atom or a group of atoms that has a net positive or negative changed anions.
Isotope
Atoms of the same element (the same number of protons) that have different numbers of neutrons. They have identical atomic numbers but different mass numbers.
Mass Number
The total number of protons and neutrons in the atomic nucleus of an atom.
Metal
An element that gives up electrons relatively easily and is typically shiny, malleable, and a good conductor of heat and electricity.
Metalloid
An element that has both metallic and non-metallic properties.
Neutron
A particle in the atomic nucleus with a mass approximately equal to that of the proton but with no charge.
Nonmetal
An element that does not exhibit metallic characteristics.
Nucleus
The small dense center of positive charge in an atom.
Periodic Table
A chart showing all the elements arranged in columns in such a way that all the elements in a given column exhibit similar chemical properties.
Proton
A positively charged particle in an atomic nucleus.