Modern definition of atomic mass unit
The mass of 1/12 part of 12C isotope of carbon is equivalent to one atomic mass unit.
Relative atomic mass
The atomic mass of an element is a relative quantity and is the mass of one atom of the element relative to 1/12 the mass of one carbon-12 atom. Thus,

Modern definition of atomic mass of an element

Gram Atomic Mass (GAM)
The atomic mass of an element expressed in grams is called the gram atomic mass of an element. It is also called gram atom.

Significance of a symbol of an element
Qualitative
- It represents a specific element.
- It represents one atom of an element.
Quantitative
- It represents how many times an atom is heavier than one atomic mass unit.
- It represents one gram - atom of an element.
- It represents how many atoms are present in one gram atom (1 mole).
