Average Atomic Mass Formula
Average Atomic Mass is defined as,of an element is the sum of the masses of its isotope, multiplied by its natural abundance.
Isotope:
The isotope are the atom of same element which have same atomic number but different mass number.
OR
Atom of the same elements having same number of protons but different number of neutron.
Atomic number:
Atomic number is The number of protons present inside the nucleus of atom.
Atomic mass:
Atomic mass is number of protons and number of neutron present inside the nucleus of atom.
Example:
- Isotope of Carbon:
Carbon has mainly two isotope represented, 126C , and 146C . Both have same atomic number that is 6 but different mass number that is 12&14.
The isotope 126C has 6 protons and 12-6 = 6 neutron in the nucleus. While
The isotope 146C has 6 protons but 14-6= 8 neutron
Formula:
- % abundance of first isotope = m1
- % abundance of first isotope = m2
- Atomic mass of first isotope= w1
- Atomic mass of first isotope= w2
OR
Formula :
Example:
Question -1 :
Calculate the average Atomic Mass of carbon 126C , % abundance is 99% and 136C . % abundance is 1%.
Solution:
Formula
- % abundance of first isotope carbon 126C 99% = m1
- % abundance of first isotope carbon136C 1%. = m2
- Atomic mass of first isotope 126C(12). = w1
- Atomic mass of first isotope136C (13). = w2
Average Atomic Mass = 12.01 amu