nuclei can contain different numbers of neutrons. Atoms of the same element that have different masses with varying numbers of neutrons are called isotopesIsotopes: Atoms of the same element that have different masses due to their varying numbers of neutrons.. Solution nuclei can contain different numbers of neutrons. Atoms of the same element that have different masses with varying numbers of neutrons are called isotopesIsotopes: Atoms of the same element that have different masses due to their varying numbers of neutrons...