Scientists Say: Atom

This is the smallest possible piece of an element

This is a depiction of what an atom might look like. The red and purple dots at the top right are protons and neutrons. The grey cloud is the place where electrons are likely to be found.

Yzmo/Wikimedia Commons (CC-BY-SA 3.0)

Atom (noun, “AA-tom”)

An atom is the smallest possible piece of a chemical element. All matter is made of groups of atoms bonded, or connected, together into molecules.

The word atom comes from the Greek word “atomos,” which means “indivisible.”  Scientists used to think that atoms could not be broken up into smaller parts. But today, we know that they can. Atoms are made of smaller parts — protons, electrons and neutrons. Protons are particles with a tiny positive electrical charge. Neutrons have no electrical charge. And electrons have a tiny negative charge.

In an atom, the protons and neutrons hang out in the center, or nucleus. The electrons travel in a cloud around the nucleus. The cloud is split into layers called orbitals, where electrons are likely to be. Atoms of different elements have different numbers of protons, neutrons and electrons. The number of protons an atom has (its atomic number) determines which element it is.

The combination of protons, neutrons and electrons in an atom give each element its unique properties. For example, the four electrons in carbon’s outermost layer give this atom the ability to bond with up to four other atoms. This makes carbon an essential building block for every living thing on Earth. The 226 neutrons in radium-226 make this atom glow in the dark.

Because they are made of smaller particles, atoms can be broken up into pieces. Once that happens, though, the pieces are no longer a part of one chemical element. Break up a carbon atom, and you no longer have carbon. So a carbon atom is still the smallest possible piece of carbon.

In a sentence

Cut a grape in half, pop it in the microwave, and you’ll get a tiny fireball of electrons and electrically-charged atoms.

Check out the full list of Scientists Say.

Bethany Brookshire is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

More Stories from Science News for Students on Chemistry