Ron Levitt Jr., age 15, of Reno, Nev., for his question:

WHAT EXACTLY IS AN ELECTRON?

An electron is a negative charge of electricity. It is the smallest known electrical charge.

In industry or in a home, electric current consists of a flow of electrons through a copper wire. The wire is the conductor. A 50 watt  house lamp has about three billion billion electrons passing through it every second.

Electrons are one of the fundamental building stones of the world. The atoms of all elements contain them.

In 1897, the British physicist Sir Joseph Thomson discovered that electrons carry electrical current. He found that they have a negative charge.

In 1907, the American physicist Robert Millikan measured this charge.

Physicists pictured electrons as tiny particles until 1927. In that year, the American physicist Clinton Davisson and the British physicist George Thomson independently discovered that electrons sometimes behave like waves.