Dalton's Atomic Theory

1. Standard/ Class/ Grade XI Chemistry
Chapter 1 Basic Concepts
Gurudatta K Wagh, gkwagh@gmail.com
Dalton’s atomic theory
Assumptions
• Matter is made up of tiny, indestructible, indivisible unit particles called atoms
• Atom is the smallest particle of an element
• Molecule is the smallest particle of a compound
• Atoms of the same element have same size, shape, mass and other properties
• Compounds are formed by the combination of different elements
• Atoms in a compound unite in small whole number ratios 1:1, 1:2, 1:3, 2:1, 2:3,
etc.
• Atoms are neither created nor destroyed in a chemical reaction
• A chemical reaction involves only the separation, combination or rearrangement
of integer number (whole numbers 1, 2, etc. not fractions 1.2, 2.5, etc.) of atoms