Answer: Equal number of protons and electrons. Example: an atom of oxygen atom has 8 electrons and 8 protons and is neutral.
Explanation:
An atom that has no charge is a neutral atom. It contains electrons equal to protons. For example: A neutral atom of oxygen has 8 protons and 8 electrons.
An atom which has charge is said be ionized. It is either positively charged or negatively charged. It is positively charge when the number of electrons is less than the number of protons. For example: contains 10 electrons and 11 protons.
And when the number of electrons is greater than the number of protons, the atom is negatively charged. For example, has 17 protons and 18 electrons. It readily accepts an electron to complete its octet.