Here's why:
* Isotopes: Isotopes are atoms of the same element that have the same number of protons (defining the element) but different numbers of neutrons. This difference in neutrons affects the atomic mass.
* Mercury's Isotopes: Mercury has 7 stable isotopes, with mass numbers ranging from 196 to 204. The most common isotope is mercury-202 (29.8% abundance).
Therefore, to determine the mass number of a specific mercury atom, you need to know which isotope you are dealing with.
If you are given a sample of mercury, it will likely contain a mixture of isotopes. The average atomic mass of mercury (listed on the periodic table) is 200.59 u, which reflects the weighted average of all the isotopes and their abundances.
