Isotope
/ˈaɪsəˌtoʊp/
Listen pronunciation
Definition
(noun) Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei. Thus, isotopes have the same atomic number but a different mass number.
Sentence Examples
The principal natural isotope of aluminium is aluminium-27.
CEFR Practice Quiz
Each ____ of an element has the same number of protons but a different number of neutrons in its nucleus.