Question

which of the following defines the atomic number of an atom? (1 point)
the number of protons
the number of neutrons
the number of valence electrons
the number of electrons, protons, and neutrons

Explanation:

The atomic number of an atom is defined as the number of protons in the nucleus of that atom. Neutrons are related to the mass number (atomic mass approximately), valence electrons are involved in chemical bonding, and the sum of protons and neutrons is the mass number, while electrons can vary in ions. So the correct option is the one about the number of protons.

Answer:

A. the number of protons (assuming the first option is labeled A, adjust label as per original if different, but based on content, the correct choice is the option stating "the number of protons")