## Shop Windows to the Universe

Become a nitrogen atom in the nitrogen cycle in our Traveling Nitrogen Classroom Activity Kit/Game. See all our games, activity kits and classroom activities.

# Electron

##### This movie shows one way of thinking about an atom. In this atom, the electrons are yellow. They zip around the outer edges of the atom. In the middle of the atom is the nucleus. It has protons (red) and neutrons (blue). Each proton and electron has an electrical charge. A proton has a positive (+) charge, an electron has a negative (–) charge. This movie isn't quite the right scale for real atom. The electrons should be smaller and much, much further away. If the nucleus was this size, the electrons would zing around in a space larger than a major sports stadium! An atom is mostly empty space. Original artwork by Windows to the Universe staff (Randy Russell).

An electron is one of the most important types of subatomic particles. Electrons combine with protons and (usually) neutrons to make atoms.

Electrons are much smaller than neutrons and protons. The mass of a single neutron or proton is more than 1,800 times greater than the mass of an electron. An electron has a mass of 9.11 x 10-28 grams.

Electrons have a negative electrical charge, with a magnitude which is sometimes called the elementary charge or fundamental charge. Thus an electron is said to have a charge of -1. Protons have a charge of the same strength but opposite polarity, +1. The fundamental charge has a strength of 1.602 x 10-19 coulomb.

A neutral atom has equal numbers of electrons and protons. The electrons in an atom swarm in a cloud around the small, dense nucleus, which is made up of neutrons and protons. The negatively charged electrons are pulled towards the nucleus by the positively charged protons. Sometimes electrons can be knocked loose from an atom, taking along their negative charge and leaving behind an ion with a net positive charge.

Electrons can dwell at various energy levels within an atom. When electrons move from one energy level to another, they either absorb or emit a photon. Electrons in different atoms have different energies associated with their energy level transitions. The different energies of photons emitted or absorbed by different elements serve as "fingerprints" that scientists can use to identify specific elements. These "fingerprints", in the form of spectra of light or photons of other wavelengths, allow us to determine, for example, that distant stars are made mostly of hydrogen.

Electrons are a type of lepton, a class of subatomic particles which also includes muons and tauons.

Electrons are often torn loose from their parent atoms. Such "free electron" can be accelerated, because of the electron's charge, to very high speeds and energies by electrical and magnetic fields. Such energetic free electrons are a form of particle radiation.

Large numbers of electrons can flow when exposed to an electrical or magnetic field. A flow of electrons is called an electrical current. We are all familiar with the flow of electricity within wires in our houses. Electrical currents can flow outside of wires as well, such as in the ion- and electron-rich layer of Earth's atmosphere called the ionosphere.

#### Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

## Traveling Nitrogen Classroom Activity Kit

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

## Photon

Light is very strange. Sometimes it is best to think of light as a series of waves. At other times, it is useful to think of light as a swarm of particles. When we think of light as particles, we call...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

One main type of radiation, particle radiation, is the result of subatomic particles hurtling at tremendous speeds. Protons, cosmic rays, and alpha and beta particles are some of the most common types...more

## Atomic Physics & Particle Physics

Atoms and the tiny particles from which they are made strongly influence the world around us. The fields of atomic physics and particle physics help us understand the life cycles of stars, the forms of...more

## The Thermosphere

The thermosphere is a layer of Earth's atmosphere. The thermosphere is directly above the mesosphere and below the exosphere. It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to...more

## Chemistry

Chemistry is the study of matter, energy, and their interactions. Chemists study the composition of substances, their properties, and how they react with each other under varying circumstances. Indeed,...more

## Saturn's Aurora

Have you ever seen the Southern or Northern Lights? Earth isn't the only planet that puts on these beautiful light shows, which are also called the "aurora". Aurora have been seen at both poles of Saturn,...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information.