Question

According to Dalton’s Atomic Theory, the smallest indivisible particles of matter is called ______.
1. molecule
2. atom
3. compound
4. element

Answer 1

Correct Answer - Option 2 : atom

The correct answer is atom.

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• In 1808, John Dalton first proposed an atomic theory of matter and he named it Dalton's atomic theory.
• Dalton’s atomic theory was able to explain the law of conservation of mass, law of constant composition, and law of multiple proportions very successfully.
• According to Dalton’s Atomic Theory:
• The smallest indivisible particle of matter is called an atom. The theory states that all the matter is composed of indestructible and indivisible building blocks called atoms.
• All atoms of a specific element are identical in mass, size, and other properties. However, atoms of different elements exhibit different properties and vary in mass and size.
• Atoms can neither be created nor destroyed. Furthermore, atoms cannot be divided into smaller particles.
• Atoms of different elements can combine with each other in fixed whole-number ratios in order to form compounds.
• Atoms can be rearranged, combined, or separated in chemical reactions.
• Hence, according to Dalton’s Atomic Theory, the smallest indivisible particles of matter are called atoms.

• Law of conservation of mass:
  • According to the law, mass can neither be destroyed nor be created in any chemical reaction.
• Law of constant proportion/ definite proportion:
  • The laws state that in a chemical substance, the elements are always present in certain proportions by mass.
• For example:
  • Oxygen & Hydrogen are present in water in a ratio of 8:1.
  • So we will obtain 1g of hydrogen and 8g of oxygen if we decompose 9g of water.
• Atom: 
  • An atom is the smallest invisible unit of matter that constitutes a chemical element.
  • Every plasma, solid, gas & liquid, is composed of ionized or neutral atoms.
  • Around 100 picometers across, atoms are extremely small.