1. An electron is in a region outside the nucleus. How will you describe an

electron?

A. Has a positive charge

B. Is larger than a proton and has no charge

C. Is smaller than a proton and has no charge

D. Has less mass than a proton and has a negative charge

➡A. Has a positive charge✨

• ➡the nucleus of an atom. Electrons in atoms exist in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron.

2. What subatomic particle has a negative charge?

A. electron

C. neutron

B. proton

D. isotopes

➡A. electron✨

➡electrons✨

• ➡A third type of subatomic particle, electrons, move around the nucleus. The electrons have a negative electrical charge. An atom usually contains an equal number of positively charged protons and negatively charged electrons.

Who discovered the electron of an atom?

A. Eugen Goldstein C. J.J. Thomson

B. Ernest Rutherford D. James Chadwick

➡C. J.J. Thomson✨

➡C. J.J. Thomson✨

• ➡During the 1880s and '90s scientists searched cathode rays for the carrier of the electrical properties in matter. Their work culminated in the discovery by English physicist J.J. Thomson of the electron in 1897.

Which scientist discovered the charged particle proton?

A. Chadwick

C. Rutherford

B. Thomson

D. Milliken

➡C. Rutherford✨

➡C. Rutherford✨

• ➡Observed as H+ by Eugen Goldstein (1886). Identified in other nuclei (and named) by Ernest Rutherford (1917–1920). , with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron.

Which of the following particles bear neither a positive nor a negative

charge?

A. electron

C. neutron B. proton

D. molecules

➡C. neutron✨

• ➡atom along with the protons. Protons and neutrons are the heavy parts of an atom. Their combined weights are called the atomic weight of an element. Electrons are so light that we say they do not have weight.