Who developed the atomic theory of matter?

Who developed the atomic theory of matter?

• A. Albert Einstein.
• B. Niels Bohr.
• C. Dmitri Mendeleev.
• D. John Dalton.

Answer: (D)

The idea that matter is made of small, indivisible units called atoms and that chemical changes come from rearranging these atoms was first proposed by John Dalton. Dalton laid out a clear atomic theory in the early 1800s: matter is composed of atoms; atoms of the same element are identical in mass and properties; compounds form from simple, whole-number combinations of atoms; and in reactions, atoms are rearranged but not created or destroyed. This framework explains why elements combine in fixed proportions and underpins modern chemistry. Other famous scientists contributed important atomic-structure ideas—Albert Einstein helped establish quantum concepts, Niels Bohr proposed a model with quantized electron orbits, and Dmitri Mendeleev created the periodic table and predicted properties of unknown elements—but the development of atomic theory as a general explanation for matter is credited to Dalton.

The idea that matter is made of small, indivisible units called atoms and that chemical changes come from rearranging these atoms was first proposed by John Dalton. Dalton laid out a clear atomic theory in the early 1800s: matter is composed of atoms; atoms of the same element are identical in mass and properties; compounds form from simple, whole-number combinations of atoms; and in reactions, atoms are rearranged but not created or destroyed. This framework explains why elements combine in fixed proportions and underpins modern chemistry. Other famous scientists contributed important atomic-structure ideas—Albert Einstein helped establish quantum concepts, Niels Bohr proposed a model with quantized electron orbits, and Dmitri Mendeleev created the periodic table and predicted properties of unknown elements—but the development of atomic theory as a general explanation for matter is credited to Dalton.