Why do mass numbers have a trailing decimal? use the following words describe for credit isotopes protons neutrons electrons in carbon 13 HELP ME

a number without a decimal are generally not significant. Isotopes are atoms of same element which have the same atomic number but different number of neutrons. Isotopes of elements are represented in the following way: In an atom, the number of protons is equal to its atomic number.. An atom of an element is neutral in nature so atom contains the same number of protons and electrons.

Explanation:

this would be about 43%