EVERYDAY SCIENCE

Detailed explanation-1: -Also known as the dalton (Da) or unified atomic mass unit (u), the AMU expresses both atomic masses and molecular masses. AMU is defined as one-twelfth the mass of an atom of carbon-12 (12C). C is the most abundant natural carbon isotope, accounting for over 98% of carbon found in nature.

Detailed explanation-2: -Thus, mass of one atom of C-12 is 1.99×10−23g.

Detailed explanation-3: -An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12. The number of protons in the nucleus of an atom determines an element’s atomic number.

Detailed explanation-4: -All the masses of the elements are determined relative to 12C. Since many elements have a number of isotopes, chemists use average atomic mass. On the periodic table the mass of carbon is reported as 12.011 amu.

Detailed explanation-5: -Naturally occurring hydrogen has three isotopes 1H1 1H2 and 1H3 and its relative atomic mass works out 1.008 rather than 1. Atomic mass of carbon is 12. Thus 1/12 mass of carbon work out as 1. It is on account of the above reason 1/12 mass of carbon is used for comparing relative atomic masses of other elements.