One isotope of iodine differs from another in __________ .

a. the number of protons
b. the number of electrons
c. the number of neutrons
d. atomic number

Verified step by step guidance

Recall the definition of isotopes: isotopes are variants of the same chemical element that have the same number of protons but differ in the number of neutrons.

Understand that the number of protons defines the element and its atomic number, so isotopes must have the same number of protons and atomic number.

Recognize that electrons can vary in ions, but isotopes specifically differ in the nucleus, not in electron count.

Therefore, the key difference between isotopes lies in the number of neutrons in the nucleus.

Conclude that the correct answer is the option indicating the difference in the number of neutrons.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isotopes

Isotopes are variants of the same chemical element that have the same number of protons but differ in the number of neutrons. This difference in neutrons results in different atomic masses but does not change the chemical properties significantly.

Atomic Number

The atomic number is the number of protons in the nucleus of an atom and defines the element. It remains constant for all isotopes of a given element, distinguishing one element from another.

Neutrons and Atomic Mass

Neutrons are neutral particles in the nucleus that contribute to the atomic mass but do not affect the charge. Variations in neutron number among isotopes cause differences in atomic mass and nuclear stability.

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