Shop Windows to the Universe

We now offer the Cool It! card game in our Science Store. Cool It! is the new card game from UCS that teaches kids about the choices we have when it comes to climate change.
This image is a model of an atom
Windows to the Universe original animation by Randy Russell.

Atoms

Atoms are the smallest size pieces that elements come in. Each atom has a small but heavy nucleus at its center. A cloud of tiny, fast-moving electrons orbit around the nucleus. The nucleus contains protons and neutrons. Most atoms have about as many neutrons as protons. A "normal" atom has the same number of electrons and protons.

The animation of an atom on this page is NOT to scale. In a real atom, the protons, neutrons, and electrons are very tiny compared to the distance between the nucleus and the electrons. Most of an atom is empty space. Atoms are incredibly small. They have sizes between 60 and 500 picometers (a picometer is 10-12 meters, or one trillionth of a meter!). The nucleus of an atom is about 100,000 times smaller than the whole atom. Almost all (more than 99%) of the mass of an atom is in the nucleus.

Sometimes two or more atoms "stick together" to form a molecule. Some molecules have atoms of just one type. For example, an oxygen molecule (O2) has two oxygen atoms. Other molecules combine different types of atoms. Methane (CH4) has one carbon atom and four hydrogen atoms.

Last modified September 15, 2010 by Randy Russell.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, classroom activities in The Earth Scientist, mineral and fossil specimens, and educational games!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Element (Chemical Element)

An element (also called a "chemical element") is a substance made up entirely of atoms having the same atomic number; that is, all of the atoms have the same number of protons. Hydrogen, helium, oxygen,...more

Molecules

Most things around us are made of groups of atoms connected together into packages called molecules. Molecules are made from atoms of one or more elements. Some molecules are made of only one type of...more

Oxygen

Oxygen (O2) is a kind of gas. A lot of the air you breathe is oxygen. That's a good thing, since we need oxygen to stay alive! About 4/5ths of the air in Earth's atmosphere is nitrogen (N2). Almost all...more

Methane - CH4

Methane is a kind of gas. There is a small amount of methane in the air you breathe. A methane molecule has carbon and hydrogen atoms in it. Methane is a greenhouse gas. That means it helps make Earth...more

Atomic Mass

One way scientists measure the size of something is by its mass. Mass is sort of like weight. Scientists can even measure very, very tiny things like atoms. One measure of the size of an atom is its "atomic...more

Atomic Number

Every atom has a nucleus. The nucleus has protons and neutrons in it. Scientists have a special name for the number of protons in an atom. They call it the "atomic number". There are almost 100 different...more

Isotope

Isotopes are different "versions" of an element. All atoms of an element have the same number of protons. All hydrogen atoms have one proton, all carbon atoms have 6 protons, and all uranium atoms have...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF