Which of the following pairs would be called isotopes?

A. Uranium-235 and uranium-238
B. Uranium-235 and plutonium-239
C. Sulfur-32 and phosphorus-32
D. hydrogen-1 and helium-4

1 answer

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses.

From the options provided:

A. Uranium-235 and uranium-238 - These are isotopes of uranium because they have the same number of protons (92) but different numbers of neutrons (143 and 146, respectively).

B. Uranium-235 and plutonium-239 - These are not isotopes because they are different elements (uranium and plutonium).

C. Sulfur-32 and phosphorus-32 - These are not isotopes because sulfur and phosphorus are different elements.

D. Hydrogen-1 and helium-4 - These are not isotopes because they are different elements (hydrogen and helium).

The correct answer is A. Uranium-235 and uranium-238.