Chemistry Regents Exam August 2022
4. Which phrase describes two atoms that contain the same number of protons but a different number of neutrons?
(1) ions of the same element (2) isotopes of the same element
(3) a mixture of different elements
(4) nuclides of different elements
Explanation: Two atoms with the same number of protons but a different number of neutrons are called isotopes. Isotopes always have the same number of protons and therefore are atoms of the same element. They differ in their number of neutrons (and therefore mass).