Name the British chemist who presented his atomic theory in 1808, on conservation of mass and law of definite proportions, which was a turning point in the study of matter.

Correct option is A

Ans. (a) John Dalton

Sol.John Dalton, a British chemist and physicist, presented his atomic theory in 1808, which was based on the law of conservation of mass and the law of definite proportions. His theory proposed that all matter is composed of tiny, indivisible particles called atoms, which combine in fixed ratios to form compounds. This theory laid the foundation for modern chemistry and revolutionized the study of matter.

Information Booster:

• Dalton’s Atomic Theory (1808) stated that atoms are indivisible and indestructible.
• Atoms of the same element are identical, but atoms of different elements vary in properties and mass.
• Compounds are formed when atoms of different elements combine in simple whole-number ratios.
• Chemical reactions involve the rearrangement of atoms, but atoms themselves are neither created nor destroyed.
• Dalton’s theory was influenced by Antoine Lavoisier’s Law of Conservation of Mass and Joseph Proust’s Law of Definite Proportions.
• Though Dalton believed atoms were indivisible, later discoveries, such as the electron (by J.J. Thomson in 1897), the nucleus (by Rutherford in 1911), and protons/neutrons, proved that atoms are made of smaller particles.
• Despite modifications, Dalton’s atomic theory remains a cornerstone of modern chemistry.

Additional Information:

• Lavoisier (b) – Known as the "Father of Modern Chemistry," he formulated the Law of Conservation of Mass, stating that mass remains constant in a chemical reaction.
• Ernest Rutherford (c) – Discovered the atomic nucleus in 1911 through his gold foil experiment and proposed the planetary model of the atom, refuting Dalton’s idea of indivisible atoms.
• Proust (d) – Introduced the Law of Definite Proportions, stating that a chemical compound always contains elements in a fixed mass ratio.