what do we call atoms of the same element that have different numbers of neutrons?

They are called isotopes.

Quick Scoop

Atoms of the same element always have the same number of protons, but they can have different numbers of neutrons in their nuclei. When that happens, those atoms are isotopes of that element.

Simple example

• Carbon-12 and carbon-14 are both carbon, so each atom has 6 protons.

• Carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons, so they are different isotopes of carbon.

In everyday chemistry, isotopes behave almost the same, but in nuclear science and dating methods (like carbon dating), those neutron differences matter a lot.

TL;DR: Atoms of the same element with different numbers of neutrons are called isotopes.

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