Question

scientists in a lab are working with two different samples of the element mercury. they know that the different samples are different isotopes. which property of the isotopes must be different? the atomic number the electric charge the element name the mass number

Explanation:

Isotopes of an element have the same atomic number (which determines the element name) and can have the same electric charge (if in the same ionic state). Isotopes differ in the number of neutrons, so their mass number (sum of protons and neutrons) must be different.

Answer:

the mass number