Question

on the periodic table, how is atomic mass represented? as an average of the mass of different isotopes as the mass of the most common isotopes as the exact mass of every atom as the masses of all protons added together

Explanation:

Atomic mass on the periodic table is calculated as the weighted average of the masses of an element's isotopes. Isotopes are atoms of the same element with different numbers of neutrons. The formula for atomic mass \( M\) is \( M=\sum_{i = 1}^{n}M_i\times a_i\), where \( M_i\) is the mass of the \( i\) -th isotope and \( a_i\) is its relative abundance. It's not just based on the most common isotope (ignores other isotopes' contributions), not the exact mass of every atom (atoms of an element have different isotopes), and not just the sum of protons (neutrons also contribute to mass).

Answer:

As an average of the mass of different isotopes.