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460
Democritus
460 BC. He was a natural philosopher who rivaled with Aristotle. He became known for his philosophies on cheerfulness and was given the nickname, “the laughing philosopher”. He was unselfish even in his dying days. He was a founder of the atom theory, stating that everything is made up of tiny invisible things that are never deleted, just changed and moved. -
Isaac Newton
He studied gases, and the possibility of atoms existing. He proposed a mechanical universe where small solid masses were in motion. He believed that there were little tiny pieces of mass that were ‘swimming’ everywhere. He began to understand that atoms or particles move and are not stationary. -
John Dalton
Work led to widespread acceptance to the idea of atoms. He decided that elements have particles that combine in simple ways. His theories: 1) All matter is made of atoms that can be combined. 2) Atoms of the same element are exactly alike. 3) Atoms of a different element are different. 4) Atoms of two or more elements can be combined to form new substances. He made tremendous contributions to the understanding of the atom, but his discoveries were not complete. -
William Crooke
In 1879, Sir William Crookes studied the effects of sending an electric current through a gas in a sealed tube. The tube had electrodes at either end and a flow of electrically charged particles moved form one of the two electrodes. This electrode was called the cathode, and the particles were known as the cathode rays. The particles were first believed to be negatively charged atoms or molecules. Subsequent experiments showed that these particles could penetrate thin sheets of material. This wo -
JJ Thomson
An English scientist found that atoms were not simple, solid spheres. He discovered electrons, which are small particles located outside of the nucleus which have a negative charge. The electron is a very important part of the atom that we put to use every day through electricity and magnets. -
Ernest Rutherford
Developed a more complete understanding to the structure of atoms. He fired a stream of positively charged particles at a thin sheet of gold foil. Most particles passed right through the gold atoms and sheet of foil. He concluded that the atoms were mostly made of space. The atom had a small, dense positively charged center that repelled the positively charge bullets. He called the center the nucleus. All of the positively charged particles were in the nucleus and the negatively charged particle -
Albert Einstein
He was the first person to show a way to prove the existence of atoms-using an ordinary microscope. He published his Special Theory of Relativity, which later led to the General Theory of Relativity. After this he was designated as the father of modern physics. He also proposed that light energy can be absorbed or emitted only in discrete packets called quanta, a provocative contradiction of the then-prevalent wave theory of light. He finally won the Nobel Prize. He also explained the equivalenc -
Niels Bohr
Proposed that electrons orbit around the nucleus. Each electron has a fixed amount of energy and that each orbits in energy levels forming rings around the nucleus. As you go away from the nucleus, energy increases. -
James Chadwick
He bombarded Beryllium atoms with alpha particles. An unknown radiation was produced. Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton. The particle became known as the neutron. With this discovery, an adequate model of the atom became available to chemists. -
Louis de Broglie
French quantum physicist, Louis de Broglie introduced his theory of particle-wave duality in 1924. The wave and particle interpretations of light and matter were seen as being at odds with one another, but de Broglie suggested that these seemingly different characteristics were the same behavior observed from different perspectives. Particles behave like waves, and waves radiation can behave like particles. It was originally a doctor’s thesis, but later advisers concluded that they could not ful -
Werner Heisenberg
He was a German theoretical physicist who made foundational contributions to quantum theory. He is best known for the development of the matrix mechanics formulation of quantum mechanics in 1925. He asserted the uncertainty principle in 1926. He also made important contributions to nuclear physics, quantum field theory and particle physics. -
Erwin Schrödinger
In 1926, Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. He used mathematical equations to describe the likelihood of finding an electron in a certain positions. This atomic model is known as the quantum mechanical model of the atom. This model does not define the exact path of an electron, but predicts the odds of the location of the electron. This model can be portrayed as a nucleus surrounded by an electron cloud. Where the cloud is most dense, the probabi
