Modern Atomic Theory

In view of new discoveries about atoms, Dalton's atomic theory was modified as given below:

• Atom is no longer indivisible as it has a complex structure of sub atomic particles (electrons, protons and neutrons).

• Atoms of the same element may posses different relative masses (isotopes).

• Certain atoms of different elements have same relative masses but their chemical properties are entirely different (isobars).

• Although the atom is composed of sub-atomic particles, it still is the smallest unit that takes part in a chemical reaction.

• The ratio in which the different atoms combine may be fixed and integral but may not always be simple.

• Atom of one element may be changed into atoms of another element (transmutation).

• The mass of an atom can be changed into energy (E = mc²) shows that atom is no longer indestructible.