Atomic Structure of Matter

The atomic structure of matter is the general idea of making use of an atom as the smallest particle of matter. However, the concept of an atom is still a theory which is still subject to change.

Development of Atomic Model

The idea development of atomic model can be roughly divided into Democritus idea, Dalton idea, Thomson idea, Rutherfor idea, Bohr idea, and Quantum Cloud idea.

Democritus Model

Around 400 BC, Greek philosophers Democritus suggested that matter can be cut into smaller pieces continuously, but at some point, the infinitesimally small piece of matter will be so timy that it could no longer be divided. This infinitesimally small piece of matter is called atom, an indivisible particle. In other words, different matter consists of different infinitesimal particles, atoms, with a void or empty space between them. Atoms of different matter are different in size, shape, mass, position, and arrangement. The idea of atom forms the preliminary theory of atomic model, although the idea of Empedocles that all matter was composed of four elements, namely, fire, air, water, and earth, was accepted at that time.
Typical timeline: Thales of Miletus → Anaxgoras and Empedocles (500-428 BC) → Empedocles (484-428 BC) → Democritus (460-370 BC) → Aristotle (384-322 BC)

Dalton Model

Around 1800, John Dalton used chemical experimental evidence to formulate the atomic model of matter. All elements of matter are composed of indivisible atoms. Atoms of same element are the same, while atoms of different elements are different. Atoms of different elements can be combined to form a compound through chemical reactions in which atoms of elements are separated, joined, or rearranged with no atoms of elements are transformed from atom of one element to atom of another element.
Typical timeline: Rodger Bacon (1214-1294) → Isaac Newton (1704) → John Dalton (1803) →

Thomson Model

Around 1897, J.J. Thomson used his discovery of the electron through cathode rays experiment to reformulate the atomic model of matter by suggested that the atom was not an indivisible particle but a plum pudding model. An atom was a spherical pudding of positively charged fluid, in which plums of negatively charged electrons are held by the electrical forces of positively charged fluid.
Typical timeline: Michael Faraday (1832) → J. Plucker (1859) → James Clerk Maxwell (1873) → Sir William Crookes (1879) → E. Goldstein (1886) → Wilhelm Roentgen (1895) → Henri Becquerel (1896) → J.J. Thomson (1897) →

Rutherfor Model

Around 1911, Ernest Rutherford used his discovery of the nucleus of atom through gold foil experiment to reconstruct the atomic model of matter by suggested that atoms consisted of a centered nucleus with small dense positive charges and negatively charged electrons were scatterly moving arround in orbit held by the positively charged nucleus through electrical forces.
Typical timeline: Marie Skodowska Curie (1898) → Ernest Rutherford (1899) → Soddy, Max Planck, Pierre Curie (1900) → Nagaoka (1903) → Abegg, Ernest Rutherford (1904) → Albert Einstein (1905) → Hans Geiger (1906) → R.A. Millikan (1909) → Ernest Rutherford (1911) →

Bohr Model

Around 1913, Neils Bohr incorporated the idea of quantum into the atomic model of matter by suggesting that electrons are moved in fixed, circular orbits around the nucleus at different energy levels in form of electron shells.
Typical timeline: Neils Bohr (1913) →

Quantum Cloud Model

There are two breakthroughs in constructing the atomic model of matter. The first one is the discovery of electrons that move in waves. And the second one is the discovery of neutron, the neutral atomic particle, by Chadwick.
Around 1926, Erwin Schrödinger used mathematical equations to represent the quantum mechanical model of the atom through using the wave function to describe all possible states of electron in an electron cloud, and to calculate the probability of finding an electron at any given location around the nucleus.
Around 1932, James Chadwick used his discovery of the neutral atomic particle, through bombarding beryllium atoms with alpha particles to reconstruct the nucleus of atomic model by suggesting that protons and neutrons are bound together to form the atomic nucleus of atom by the nuclear force.
Typical timeline: H.G.J. Moseley (1914) → Aston, Ernest Rutherford (1919) → Neils Bohr (1922) → Louis Victor de Broglie (1923) → Werner Heisenberg, Max Born and Erwin Schodinger (1925) → Werner Heisenberg (1927) → Erwin Schrodinger, Paul Dira (1930) → James Chadwick (1932) →

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