When the proton number and electron number are unequal, the atom or molecule:

• A. remains electrically neutral
• B. forms a covalent bond
• C. has a net electric charge and is called an ion
• D. becomes radioactive

Answer: (C)

Verified step by step guidance

1. Understand that the proton number (atomic number) represents the number of positively charged protons in the nucleus of an atom, while the electron number represents the number of negatively charged electrons surrounding the nucleus.
2. Recall that in a neutral atom, the number of protons equals the number of electrons, so their charges balance out, resulting in no net electric charge.
3. When the proton number and electron number are unequal, the balance of positive and negative charges is disturbed, causing the atom or molecule to carry an overall positive or negative charge.
4. An atom or molecule with a net electric charge due to unequal numbers of protons and electrons is called an ion.
5. Therefore, the correct conclusion is that when proton and electron numbers differ, the species has a net electric charge and is called an ion.