Question

which of the properties is the unique, defining property of atoms of a particular element?
○ charge
○ atomic number
○ isotope
○ atomic mass

Explanation:

• Charge: Atoms can have different charges (ions) and the same element can form ions with different charges, so charge is not unique to define an element.
• Atomic number: The atomic number (number of protons) is unique for each element. All atoms of a particular element have the same atomic number.
• Isotope: Isotopes are variants of an element with different atomic masses (due to different numbers of neutrons), so isotope is not a defining property of the element itself but a variation within the element.
• Atomic mass: Different isotopes of the same element have different atomic masses, so atomic mass is not unique to define an element.

Answer:

B. atomic number