EVERYDAY SCIENCE

Detailed explanation-1: -Summary. Dalton’s atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties. Dalton based his theory on the law of conservation of mass and the law of constant composition. The first part of his theory states that all matter is made of atoms, which are indivisible.

Detailed explanation-2: -The modern atomic theory, proposed about 1803 by the English chemist John Dalton (Figure 4.2. 1), is a fundamental concept that states that all elements are composed of atoms.

Detailed explanation-3: -The following are the postulates of his theory: Every matter is made up of atoms. Atoms are indivisible. Specific elements have only one type of atoms in them. Each atom has its own constant mass that varies from element to element.

Detailed explanation-4: -The kinetic-molecular theory explains the states of matter, and is based on the idea that matter is composed of tiny particles that are always in motion. This theory helps explain observable properties and behaviors of solids, liquids, and gases.

Detailed explanation-5: -J.J. Thomson’s experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged “soup."