Advertisement Upgrade to remove ads

atomic mass

the average mass of one atom of an element

periodic table

A chart of the elements showing the repeating pattern of their properties


The central core of an atom containing protons and usually neutrons


positively charged particle in the nucleus of an atom


A small particle in the nucleus of the atom, with no electrical charge


A tiny, negatively charged particle that moves around the nucleus of an atom

atomic mass unit (amu)

a unit used to measure the mass of particles in atoms; a proton or neutron has the mass of 1 amu

atomic number

the number of protons in the nucleus of an atom

chemical symbol

a one or two letter representation of an element


elements in the same vertical column of the periodic table; also called family


elements in the same vertical column of the periodic table; also called group


a horizontal row of elements in the periodic table

valence electron

One of the electrons farthest away from the nucleus of the atom; these electrons are involved in a chemical reaction.


a term used to describe material that can be rolled or hammered into shapes


a term used to describe a material that can be pulled out into a long wire


a substance that transmits heat or electricity easily


a characteristic of those metals that are attracted to magnets and can be made into magnets


the ease and speed with which an element combines, or reacts, with other elements and compounds


the gradual wearing away of a metal element due to a chemical reaction


a mixture of two or more metals

alkali metal

an element in group 1 of the periodic table

alkaline earth metal

An element in group 2 of the periodic table

transition metal

An Element in group 3 through 12 of the periodic table


an element in the first row of the rare earth elements in the periodic table


an element in the second row of the rare earth elements in the periodic table


An Element that lacks most of the properties of metals

diatomic molecule

a molecule composed of two atoms

halogen family

the elements in group 17 of the periodic table

noble gas

an element in group 18 of the periodic table


an element that has some characteristics of metals and some characteristics of nonmetals


an element that can conduct electricity under some conditions


a state of matter in which atoms are stripped of their electrons and the nuclei are packed closely together

nuclear fusion

the process in which smaller nuclei combine into larger nuclei, forming heavier elements


An explosion of a massive star

Flickr Creative Commons Images

Some images used in this set are licensed under the Creative Commons through Click to see the original works with their full license.

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording