Three important concepts of Chemistry-
Atom – An atom is a particle of matter that uniquely defines a chemical element. An atom consists of a central nucleus that is surrounded by one or more negatively charged electrons. The nucleus is positively charged and contains one or more relatively heavy particles known as protons and neutrons.
Moles- The mole, symbol mol, is the SI unit of amount of substance of a specified elementary entity, which may be an atom, molecule, ion, electron, any other particle or a specified group of such particles; its magnitude is set by fixing the numerical value of the Avogadro constant to be exactly 6.022 141 29 × 1023 when it is expressed in the SI unit mol–1
Molecular Mass – The molecular mass of a substance is the sum of atomic masses of all the atoms in a molecule of the substance. It is used for those substances whose constituent particles are molecules.
For example:
The moleculear mass of CO2=(1×atomic mass of carbon)+(2×atomic mass of oxygen)
12+2×16
12+32=44u
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