John Dalton proposed the atomic theory in 1808 which describe matter in terms of atomic and atomic properties. In 1904, Thomson pudding model was proposed; then in 1911,Rutherford model was proposed. And then in 1913, after working in Rutherford laboratory, Bohr proposed an another model.
But interestingly, in Bhagwat Puran these concepts of atomic and molecular physics are discussed. Atom is termed as Parmanu and molecule are Anu in Vedic texts. These verses from Bhagwat Puran discuss about atoms and molecules:
Bhagvat Puran 3.11.1
चरमः सद्विशेषाणामनेकोऽसंयुतः सदाІ
परमाणुः स विज्ञेयो नृणामैक्येभ्रमो यतःІІ
The minutest particle of a material, which is not further divisible, not even been combined with other particle and hence which exist eternally i.e. in casual state, is known by the name Parmanu. Combination of these Parmanu creates material although it is misunderstood by people and is an illusionary notion of unit.
Thus, minutest particle(indivisible) in its casual state(non-bonded) is called Parmanu(atom). Combination of these Parmanu here refers to the atomic bonding.
Bhagvat Puran 3.11.2
सत एव पदार्थस्य स्वरूपावस्थितस्य यत्І
कैवल्यं परममहानविशेषो निरंतरःІІ
The entire range of material substance is taken as unspecified and undifferentiated whole before it undergoes ultimate transformation, that is it return to its ultimate source (Parkriti).
When atoms stay in their own form(no bond formation) without forming different substance, they are called unlimited oneness. There are different bodies in physical form, but the atoms for complete manifestation themselves.