AP BIOLOGY

Detailed explanation-1: -The number of protons in the nucleus of the atom is equal to the atomic number (Z). The number of electrons in a neutral atom is equal to the number of protons. The mass number of the atom (M) is equal to the sum of the number of protons and neutrons in the nucleus.

Detailed explanation-2: -When an atom has an equal number of electrons and protons, it has an equal number of negative electric charges (the electrons) and positive electric charges (the protons). The total electric charge of the atom is therefore zero and the atom is said to be neutral.

Detailed explanation-3: -Answer and Explanation: The mass number used to identify a particular atom’s isotope is exactly equal to the total number of protons and neutrons in an atom.

Detailed explanation-4: -Therefore, atomic number is equal to number of protons or number of electrons.

Detailed explanation-5: -atomic number, the number of a chemical element in the periodic system, whereby the elements are arranged in order of increasing number of protons in the nucleus. Accordingly, the number of protons, which is always equal to the number of electrons in the neutral atom, is also the atomic number.