The atomic number of oxygen is 8, because oxygen has

a. electrons in eight shells.

b. an atomic mass of 8.

c. a second shell with eight electrons.

d. eight protons in the nucleus

The answer is D. Oxygen has 8 protons in its nucleus.

d. eight protons in the nucleus

Atomic number is the number of protons inside the nucleus of an atom.

Electron is part of all matter that surrounds us. J. J. Thompson received the Nobel Prize for his discovery of electron in the year 1906. The electron is subatomic particles that have a negative electric charge. The mass of an electron is approximately 1/1836 of a proton.