Question

why atomic mass is an average vàlue​

Answer 1

Answer:

The atomic mass is the average number of protons and neutrons for all natural isotopes of an element. It is a decimal number.

Explanation:

Atomic Mass and Mass Number Example :

Hydrogen has three natural isotopes: 1H, 2H, and 3H. Each isotope has a different mass number.

1H has 1 proton. Its mass number is 1. 2H has 1 proton and 1 neutron. Its mass number is 2. 3H has 1 proton and 2 neutrons. Its mass number is 3. 99.98% of all hydrogen is 1H 0.018% of all hydrogen is 2H 0.002% of all hydrogen is 3H Together, they give a value of atomic mass of hydrogen equal to 1.0079 g/mol.

Answer 2

Answer:

There are different isotopes for different elements

Explanation:

The mass of each of the isotopes of an element are added with their percentage each then they are divided by 100

Example boron 11 is 80 % boron 10 is 20%

Total mass of boron 10 is 20*10

Total mass of boron 11 is 80*11

Atomic mass is (20*10)+(80*11)/100

Which is 10.8 and it is rounded off as 11 in the periodic table