What is an isotope? (3 points)

Question

The geologic age of a fossil, or a geologic event or structure expressed in units of time, usually years. Also known as actual age.
Two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.
The time required for half of the atoms of a
• radioactive substance to break down into other elements.

Answer 1

An isotope is defined as:

Two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.

This definition highlights that isotopes of an element have the same atomic number (protons) but differ in atomic mass due to the variation in neutrons.