Atom

Atom

• Ancient Greek philosopher Democritus: Proposed that matter consists of tiny, indivisible particles called atoms.

• Etymology: The term "atom" originates from the Latin word "Atomos," signifying indivisible.

• John Dalton's Atomic Theory (early 19th century):

  • All matter is composed of very small, indivisible particles known as atoms.

• Late 19th Century Perception: Atoms were considered indivisible.

• Early 20th Century Discoveries: Experiments by Goldstein, J.J. Thomson, Rutherford, Bohr, and others revealed that atoms comprise subatomic particles such as electrons, protons, and neutrons.

• Definition of an Atom:

  • The basic unit of matter.

  • The smallest unit of an element that retains its chemical properties.

  • Composed of a nucleus (protons and neutrons) surrounded by a cloud of electrons in orbitals.

• Atomic Structure:

  • Nucleus: Contains protons and neutrons.

  • Electrons: Exist in a cloud surrounding the nucleus within orbitals.

• Significance of Protons: The number of protons in the nucleus determines the element and its properties.

• Molecule Formation: Atoms combine in various ways to form molecules, which constitute all substances in the universe.

• Subatomic Particles:

  • Electrons

  • Neutrons

  • Protons

• Key Components:

  • Nucleus (central core of the atom)