Around 400 B.C.E., the Greek philosopher Democritus introduced the idea of the atom as the basic building block matter. Democritus thought that atoms are tiny solid particles that are surrounded by empty space and constantly moving at random.
Dalton's Atomic Theory. 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties. 3) Compounds are formed by a combination of two or more different kinds of atoms-1803
In 1897, J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged.Thomson realised that the accepted model of an atom did not account for negatively or positively charged particles.
Niels Bohr, a Danish scientist, explained this line spectrum while developing a model for the atom: The Bohr model shows that the electrons in atoms are in orbits of differing energy around the nucleus (think of planets orbiting around the sun). Just like that.-1913
In 1926 Erwin Schrödinger, an werner heisenberg physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.
An atom a fundamental piece of matter. An atom itself is made up of three tiny kinds of particles called subatomic particles: protons, neutrons, and electrons. The protons and the neutrons make up the center of the atom called the nucleus and the electrons fly around above the nucleus in a small cloud.