Which property of an atom's model allows someone to identify the element it represents?

• A. The total mass of the atom
• B. The number of protons in the nucleus
• C. The arrangement of electrons in energy levels
• D. The number of neutrons in the nucleus

Answer: (B)

Verified step by step guidance

1. Understand that an atom is defined by its subatomic particles: protons, neutrons, and electrons.
2. Recall that the total mass of an atom depends on both protons and neutrons, but different atoms can have the same mass number (isotopes).
3. Recognize that the number of neutrons can vary within atoms of the same element, leading to isotopes, so neutrons do not uniquely identify the element.
4. Know that the arrangement of electrons affects chemical behavior but does not define the element itself, as electrons can be gained or lost in ions.
5. Identify that the number of protons in the nucleus, called the atomic number, uniquely determines the element and distinguishes it from all others.