Question

How do isotopes relate to average atomic mass?

Answer 1

The average atomic mass of the chemical element is the sum of the atomic mass of each isotope each multiplied by the natural abundance value. The isotopes of chemical elements have similar numbers of protons but different numbers of neutrons.

Complete step by step answer:
Atoms present in the same element have different numbers of neutrons present in the nucleus like helium atoms can contain either one or two neutrons but the number protons are two. These different types of helium atoms differ in their masses and are called isotopes. The isotopes are defined as compounds of the same element which have similar atomic number but different mass number. For any given isotope the sum of the number of protons and the number of neutrons present in the nucleus is called the mass number. Each proton and each neutron weigh one atomic mass unit (amu). Adding the number of protons and neutrons and multiplying it with 1 amu, the mass of the atom can be calculated.
The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance value. Natural abundance is the decimal related to the percent of atoms of that element which is of given isotope.
The formula to calculate the average atomic mass is shown below.
$Average\;atomic\;mass = {F_1}{M_1} + {F_2}{M_2} + ...... + {F_n}{M_n}$
Where,
F is the fraction representing the natural abundance of the isotope
M is the mass number of the isotope
This is how the isotopes is related to the average atomic mass

Note: The average atomic mass value of an element can be identified on the periodic table which is present under the elemental symbol. When the value of natural abundance of various isotopes of an element is given then it is simple to calculate the average atomic mass.