Question

1. what are two characteristics atomic isotopes must have in common: b)_

Explanation:

Isotopes are atoms of the same element. They have the same number of protons which defines the element, and thus the same atomic number. Chemical properties are mainly determined by the number of electrons, which is equal to the number of protons in neutral atoms, so isotopes also have similar chemical properties.

Answer:

a) Number of protons
b) Chemical properties