Atomic number?

Atomic number?

• A. The mass of the atom
• B. The number of protons in the nucleus of an atom
• C. The total number of electrons in the atom
• D. The number of protons and neutrons in the nucleus of an atom

Answer: (B)

Atomic number is the number of protons in the nucleus. This fixed count identifies the element and places it on the periodic table. While a neutral atom has the same number of electrons as protons, the atomic number itself comes from protons, not electrons. The total mass of an atom comes from protons plus neutrons (mass number), not just protons. The total number of electrons relates to the atom’s charge and can differ in ions, and the combination of protons and neutrons gives the mass number, not the atomic number.

Atomic number is the number of protons in the nucleus. This fixed count identifies the element and places it on the periodic table. While a neutral atom has the same number of electrons as protons, the atomic number itself comes from protons, not electrons. The total mass of an atom comes from protons plus neutrons (mass number), not just protons. The total number of electrons relates to the atom’s charge and can differ in ions, and the combination of protons and neutrons gives the mass number, not the atomic number.