The Atom and Nuclear Chemistry Part 1

Evolution of atomic theory

Evolution of atomic theory

Democritus

An ancient Greek philosopher (460BC-370BCE) known as "The Mocker" and "The Laughing Philosopher," co-originator of the concept of "atomos," proposing that physical substances are made of tiny, indivisible particles.

Atomos

A term meaning "uncuttable," used by Democritus to describe the smallest units of matter that make up different substances.

Aristotle

A Greek philosopher (384 BC - 322 BCE) who proposed the four basic components of matter:fire, air, earth, and water. (WAS WRONG)

John Dalton

An English scientist (1766-1844) who published the first atomic theory in 1803 and contributed to the development of the atomic model.

All five postulates of atomic theory.

• The matter is made up of tiny indivisible particles called atoms.

• Atoms can neither be created nor destroyed.

• Atoms of a given element are identical in size, mass, and other properties.

• Atoms of different elements differ in size, mass, and other properties.

• Atoms combine in simple whole-number ratios to form compounds. In chemical reactions, atoms are combined, separated, or rearranged.

J.J Thompson

A physicist (1856-1940) who discovered the electron in 1897 and proposed the Plum Pudding Model of the atom.

Plum pudding model

Cathode Ray Tube

An experimental apparatus used by J.J. Thomson to determine the charge-to-mass ratio of cathode rays, leading to the discovery of the electron.

Ernest Rutherford

A physicist (1871-1937) known for the Gold Foil Experiment, which led to the discovery of the atomic nucleus and the nuclear model of the atom. Found and provided evidence for protons predicted but could not prove neutrons

Rutherford model

Gold Foil Experiment

An experiment conducted by Rutherford that demonstrated the existence of a small, dense nucleus within the atom, as most alpha particles passed through the foil while some were deflected.

Neutrons

Neutral particles discovered by James Chadwick in 1932, predicted by Rutherford to exist in the nucleus alongside protons.

Niels Bohr

A physicist (1885-1962) who developed the "Planetary" Model of the atom in 1913, introducing the concept of quantized energy levels.

Bohr model

Atomic Notation

A system that uses symbols to represent elements, where the atomic number (Z) indicates the number of protons, and the mass number (A) is the total number of protons and neutrons.

Isotopes

Atoms of the same element that have different numbers of neutrons, resulting in different mass numbers but the same atomic number.

Atomic Mass

The weighted average mass of all known isotopes of an element, taking into account the percent abundance of each isotope.