Which notations represent atoms that have the same number of protons but a different number of neutrons?
(1) H-3 and He-3
(2) S-32 and S-32
(3) Cl-35 and Cl-37
(4) Ga-70 and Ge-73
Answer and Explanation: Choice 3 is the correct answer choice
Atoms of the same element that have the same number of protons but a different number of neutrons are called isotopes. Whenever we see an element symbol followed by a dash and a number, that number represents the mass of the element. Choice 1 is incorrect since H and He are different elements and therefore have different numbers of protons. Choice 2 is incorrect since these are two identical atoms with the same number of protons and neutrons. Choice 4 is incorrect since Ga and Ge are different elements. Choice 3 is correct since both are atoms of Cl and therefore have the same number of protons. Yet, their masses are different and thus the number of neutrons differ as well.
Transformation Tutoring chemistry tutors are passionate about chemistry and helping our students learn. We love to see our students ace their tests. For more information, please call 646-407-9078