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100
Kanada
• Anywhere from 300 – 700BC
• It is believed Kanada developed this theory on his own, with no influences from any other scientists
• Kanada realized there is a point where matter can't be any made any smaller. He named this invisible matter 'anu.' He thought atoms joined with each other to create change, and ultimately believed Ishvara, a Hindu God, caused these changes.
• Kanada’s theory, although on the right track, really had no impact on the simple people of India. -
100
Empedocles
• 490 – 430BC
• Empedocles believed that each atom was made up of earth, water, fire, or air. He believed that combinations of such were what made up the universe
• Empedocles' theory of 'water, ear, fire and air' was adapted and further studied by many scientists' during his time. While we don’t follow Empedocles’ theory today, his beliefs got many scientists wondering about ‘what is everything we have made up of?' His work influenced Lavoisier Antoine nearly 2000 years later. -
100
Democritus
• 460BC – 370BC
• Was influenced by his mentor, Leucippus
• Democritus believed that atoms differed in size, shape, mass, position, and arrangement. Their shape decided how they reacted to the world around them; eg: Oils are made of very fine, small atoms that can easily slip past each other. His main contribution was that atoms can't be made or destroyed.
• Democritus' theory that atoms can't be created or removed founded the basis of modern understanding of the atom. -
100
Aristotle
• 284 – 322BC• Aristotle is not believed to have been influenced by any other man, in fact, Aristotle was very much against the theories of other scientists at that time• Aristotle believed that atoms were made up of water, earth, fire and air. He also believed that there were two forces in the atom, harmony and conflict, and that these were what determined if something was ‘good’ or ‘bad’• While we do not believe Aristotle’s theories today, it did have a big impact on the people at that time -
pierre gassendi
• 1592 – 1655• Was influenced by the old Greek theories on atoms• Believed that the structure of anything is based on the unstoppable, incessant, forever-in-motion atoms• This began to get scientists back on track of ‘atoms’ after they were forgotten -
Antoine Lavoisier
• 1743 – 1794
• Influenced by the discoveries of Empedocles
• Antoine made the statement that there were substances that couldn’t be broken down any further by chemical changes. He also said that even when matter changes it's form or shape, it's mass will stay the same
• This discovery ultimately gave us ‘elements’ -
Joseph proust
• 1754 – 1826• Joseph was the first to say that there was a fixed proportion in all elements. For example, if part of water had 4 grams of hydrogen and 32 parts oxygen, two parts of water would have 8 grams of hydrogen and 64 parts oxygen. The ratios always stay the same.• At first, Joseph’s theory was not accepted, but now we follow his theory. -
John Dalton
• 1766 – 1844
• Was influenced by Elihu Robinson Quaker, who taught him Latin, Greek, French, science and maths
• Everything is made of atoms. All of the atoms of one element are the same weight, and will always be the same weight. Chemical reactions are the results of the atom's neautrons, protons and electrons being rearranged.
• Dalton got a great people to think about atoms after the atomic theories were forgotten during the dark ages. -
Henry Gwyn-Jeffreys Moseley
• 1887 - 1915
• Moseley made an x-ray spectra and used it to measure the x-rays produced by different kinds of metal. This information meant the scientist could understand how many positive charges there were in the center (nucleus) of an atom.• This invention means we now have a unit of measurement known as an atomic number -
Niels Bohr
• 1885 – 1962
• Was influenced by Rutherford’s atomic theory. He was actually a student of the great Rutherford.
• Made up the basic model of the atom with a nucleus in the center and electrons orbiting it. Applied previous theory (quantum) to Rutherford’s theory and proposed that electrons orbit the nucleus depending on their angular momentum.
• This model went on to help Schrödinger discover his famous equation. In science classes today, we study the same model of the atom that Bohr invented -
Joseph John Thomson
• 1856 – 1940• Was influenced by the invention of the X-ray • Thomson was the first to say that atoms had positive and negative particles. He created an experiment to show the negative particles, which he decided to name electrons. This experiment proved that hydrogen has 1 electron. • Today, we still believe and teach Joseph’s theory on electrons. We also believe and use his findings on hydrogen’s electron. -
Ernest Rutherford
• 1871 - 1937• Was influenced by Alexander Bickerton, who looked after him at Canterbury College and really got him into physics.•Rutherford found that most of an atom is empty space, through the now famous ‘gold foil’ experiment. Rutherford fired an alpha particle at a thin gold sheet, and 7999 times out of 8000, the particle passed through!
•Today we still follow and develop Rutherford’s theory on the atom -
Erwin Rudolf Schrödinger
• 1887 – 1961• Was influenced by the work of Rutherford and Bohr. • Took Bohr’s atomic model one step further and developed an equation to find out or predict where the electrons could be found• Scientists commonly use the Schrödinger equation all around the world -
James Chadwick
• 1891 – 1974
•It is not known who influenced James Chadwick
• By performing a complex experiment where he created a beam with high penetrating power and discovered that, since it wasn’t affected by electric or magnetic fields. This meant that some element of the beam had negative particles, and James concluded that they were part of the atom. He named the negative particles inside the atom 'neutrons'
• This theory stuck, and today we still believe atoms are, in part, made up of neutrons. -
Werner Heisenburg
• 1901 – 1976• Was influenced by the work of Schrodinger• Developed a theory that electrons don’t always travel in neat patterns. He studied the patterns of atom’s electrons through mathematics, developing a way of finding a number of electrons in an atom.• This gave scientists a chance to determine the different kinds of atoms through the number of available electrons for bonding.
