Question

1. circle the letters that identify quantities that are always equal to an elements atomic number.

a. number of nuclei
b. number of protons
c. number of neutrons
d. number of electrons

Explanation:

• The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element.
• In a neutral atom (which is the most common state when not in an ionic or other charged state), the number of electrons is equal to the number of protons. This is because the positive charge of the protons is balanced by the negative charge of the electrons.
• The number of nuclei is not related to the atomic number. A nucleus is a single entity per atom.
• The number of neutrons can vary for atoms of the same element (isotopes). For example, carbon - 12 has 6 neutrons and carbon - 14 has 8 neutrons, but both have an atomic number of 6 (6 protons).

Answer:

b. number of protons, d. number of electrons