Explain the need for a reference atom for atomic mass give some information about two reference atoms
Answers
Atomic mass is the sum of electron and neutron in atoms numbers of atoms are present in the atomic mass hands to determine atomic number the reference of atomic mass is needed. .
1) The mass of an atom is concentrated in its nucleus and it is due to the protons (p) and neutrons (n) in it.
2) An atom is very very tiny. It was not possible to measure atomic mass accurately. Therefore, the concept of relative mass of an atom was formed.
3) To express relative mass of an atom, reference of atom is considered. The two reference atoms were as follows:
a) Hydrogen (H) atom: The hydrogen atom is the lightest. The relative mass of a hydrogen atom is 1 which has only 1 proton in its nucleus. On this scale, the relative atomic mass of many elements comes out to be fractional. Therefore, carbon is selected as a reference atom.
b) Carbon (C) atom: The carbon atom is selected as reference atom. In this scale, the relative mass of a carbon atom is accepted as 12.
4) The relative atomic mass of 1 hydrogen (H) atom compared to the carbon (C) atom becomes 12× 1/ 12 i.e. '1'.