2.1 THEORIES AND EXPERIMENTS RELATED TO STRUCTURE OF ATOMS

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Introduction

The idea of Greeks about Matter: Ancient Greek philosopher Democritus suggested that matter is composed of tiny indivisible particles called atoms.

Derivation of word Atom: The name atom was derived from the Latin word 'Atomos' meaning indivisible.

Atomic Theory: At the beginning of the 19th century John Dalton put forward Atomic Theory. According to it 'all matter is made up of very small indivisible particles called atoms. Till the end of the 19th century, it was considered that the atom cannot be subdivided.

Sub Atomic Particles: However, at the beginning of the 20th-century experiments performed by Goldstein, J. J. Thomson, Rutherford, Bohr, and other scientists revealed that the atom is made up of subatomic particles like electrons, protons, and neutrons. Properties of these subatomic particles will be discussed in this chapter.

Theories & Experiments Related to Structure of Atoms

Dalton's Atomic Theory:

At the beginning of the 19th century, John Dalton put forward Atomic Theory.

According to it, all matter is made up of very small indivisible particles called atoms.

  • All matter is composed of atoms.
  • An atom is an indivisible, hard, dense sphere.
  • Atoms of the same element are alike.
  • They combine in different ways to form compounds.

Note:

In the light of Dalton's atomic theory scientists performed a series of experiments, but in the late 1800s and early 1900s scientists discovered new subatomic particles.

Contribution of J.J Thomson:

J.J Thomson (1856-1940) was a British physicist. He was awarded the 1906 Noble Prize in physics for the discovery of electrons and for his work on the conduction of electricity in gases.

  • He discovered electrons.
  • He determined the e/m ratio of the electron.
  • He put forth plum putting theory.

Plum Pudding Theory:

Thomson put forth his "plum pudding theory". He postulated that atoms were the solid structures of positively charged with tiny negative particles stuck inside. It is like a plum in the pudding.

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Hello, this is Misbah ud Din a student of STEM. This is my blog chemisTREEpk which provides a vast knowledge about Chemistry(and sometimes other sciences) fully free.

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