Atomic Structure Basics

Atomic Structure

• An atom consists of a nucleus (centre) containing protons (positively charged) and neutrons (neutral), surrounded by negatively charged electrons.
• The study of atomic structure provides insight into chemical reactions, bonds, and physical properties.

History of Atomic Structure

• Democritus first proposed that matter is composed of atoms.
• John Dalton proposed the first scientific theory of atomic structure in the 1800s.

Subatomic Particles

• The discovery of subatomic particles has led to many other discoveries and inventions.
• The atomic structure of an element is made up of protons, electrons, and neutrons.

Atomic Number and Ions

• The atomic number of an element describes the total number of protons in its nucleus.
• Neutral atoms have equal numbers of protons and electrons.
• Atoms may gain or lose electrons to form ions, increasing their stability.

Atomic Models

• Many scientists, including John Dalton, J.J. Thomson, Ernest Rutherford, and Niels Bohr, have contributed to the development of atomic models.
• Each model has its own merits and demerits.

Dalton's Atomic Theory

• John Dalton suggested that all matter is made up of atoms, which are indivisible and indestructible.
• Atoms of different elements differ in size and mass.
• Dalton's atomic theory explained the Laws of chemical reactions, including the Law of conservation of mass and the Law of constant properties.

Demerits of Dalton's Atomic Theory

• The discovery of particles inside atoms led to a better understanding of chemical species.

Thomson Atomic Model

• J.J. Thomson proposed a model describing the atomic structure in the early 1900s.
• His work is based on the cathode ray experiment, which led to the discovery of "electrons".