Evolution of the Atomic Theory



460 BC - 370 BC

Democritus was less of a scientist and more of a philosopher who didn't do experiments but he believed that his model of an atom was correct. He never could have done experiments because of the time period he was in. According to his writings Democritus acquired his model from the moon and it's shape.

Did you Know?-Democritus was known as the laughing philosopher, this is because he emphasized the value of cheerfulness at work.

John Dalton

1803 - 1844

John Dalton's atomic theory had 4 parts. First, all matter is made of atoms. Atoms are indivisible and indestructible. Her also found out that all atoms of an element look the same in mass and properties. He also discovered that compounds are made by a combination of two or more different types of atoms. Lastly he discovered that a chemical reaction is a really just a different assortment of atoms. We have now discovered that atoms can be destroyed by via nuclear reactions but not by chemical reactions. Also, there are different kinds of atoms (categorizing them by their masses) within an element that are known as "isotopes", but isotopes of the same element have the same chemical properties.
Furthermore, John Dalton was born in Eaglesfield, England, on September 6, 1766, to a Quaker family. As a child, Dalton was really looking forward to a formal education, but his family was really poor. It was obvious that he would need to help out with the family's debt from a young age.During the earlier part of his career, he had discovered that he had red-green color blindness. In the 1800s, he was the first scientist to explain the behavior of atoms in terms of the measurement of weight. Dalton's had an interest in gasses. While studying the nature and structure of a chemical of air in early 1800s, Dalton learned that it was not a chemical makeup as other scientists had believed. Instead it was a mechanical system with a structure made up of small individual particles that used pressure applied by each gas on its own.

Did you Know?- John Dalton was actually a quaker, so he valued his faith very much.

Ernest Rutherford

1871 - 1937

Ernest Rutherford had a very structured childhood as well as his overall life. Born in New Zealand in 1871, he went to government schools at a young age and then went to Nelson Collegiate School when he was only 16. He was awarded a University Scholarship to go to the University of New Zealand. Here he proceeded to Canterbury College where he graduated M.A. with a double first in mathematics and physical science. After this he did some research work for the college for a short time, this leads to him receive his B.Sc. degree. In 1894 he was given an 1851 Exhibition Science Scholarship that allowed him to Trinity College in Cambridge and would work under J.J. Thomson. Then in 1897 he was awarded the B.A. Research Degree and the Coutts-Trotter Studentship of Trinity College. During his time, Rutherford was alive for World War 1 and Hitler's rise to power. His intelligence caused him to travel all over the world, he moved to Montreal in order to take the position of the Macdonald Chair of Physics. In 1907 Rutherford moved to England to take the role of the Langworthy Professor of Physics at the University of Manchester(succeeding Sir Arthur Schuster at the time). In 1919 he was requested to follow Sir Joseph Thomson and be the Cavendish Professor of Physics at Cambridge, during this time he became the Chairman of the Advisory Council, H.M. Government, Department of Scientific and Industrial Research; Professor of Natural Philosophy, Royal Institution, London; and Director of the Royal Society Mond Laboratory, Cambridge. Rutherford continued working in Cambridge for the rest of his life until he died in 1937. Rutherford used alpha rays and radium emanation to study the atomic theory, what he found changed the view of the atom forever. Executing an experiment known as the Gold Foil Experiment, Rutherford concluded that the particles within the atom(protons, neutrons, and electrons) aren't in the plum pudding model previously thought(the atom was a circle with all of the particles floating inside). The particles are actually concentrated in the center of the atom, he found that protons and neutrons lie in this concentrated area, the nucleus, and electrons orbit around the nucleus. Rutherford obtained an abundance of awards for his work some of these include being knighted in 1914, being granted to be in the Order of Merit, he was given the Nobel Prize in 1908, and receiving honorary degrees from 20 colleges. One of these universities being the Ivy League school Yale. Rutherford continued his work throughout his life till the day he died on October 19, 1937, his remains were burned and lay near some other extraordinary scientists.

Ernest Rutherford was a very awarded scientists who saw that atoms have a nucleus where the protons and neutrons are held. Rutherford used scattering alpha rays to find that protons and neutrons resided in one place, in the middle of the atom. This then led him to his theory of a nucleus in the center of the atom, to prove this he conducted an experiment, the gold foil experiment. In this, small particles were shot at a thin piece of gold, Rutherford saw that a small amount was condensed in one area. He then concluded that atoms all have a nucleus that hold particles instead of them just being scattered amongst the atom.
Rutherford’s atomic model looked similar to Erwin Schrodinger’s, there was a nucleus in the center of the atom that held all of the protons and the neutrons. The electrons were floating around the nucleus in a random order(later proved that the exact placement/paths cannot be told). When labeling the electrons, protons, and neutrons, you label the electrons with a minus(-), the protons with a plus(+), and the neutrons with nothing( ). This is because each particle has a different charge, electrons have a negative charge(1-), protons have a positive charge(1+), and neutrons have a neutral charge(0).

Did you Know?- There is actually an element in the periodic table, number 104 Rutherfordium.

Erwin Schrodinger

1887 - 1961

Erwin Schrödinger was born in Vienna in 1887 and lived a well rounded life. Homeschooled to the age of ten, he was very fluent in German and English. During Schrödinger's time, Hitler rose to power, he served as an artillery officer in World War One, and was alive in World War Two. He had a very broad education; learning chemistry, then moving on to Italian paintings and botany. He not only had a passion for the sciences, but for literature as he spent his time agonizing over ancient grammar as well as German poetry. He was in school from 1906 to 1910 at the University of Vienna, which during this time he became a master of physics. Schrödinger moved to Berlin in 1927 to be Planck's successor. Due to Hitler’s rise to power and Schrödinger’s dislike to the Nazi ways, Schrödinger moved to England to hold a fellowship at Oxford. In 1938 Austria was being annexed by Germany which caused Schrödinger to have to escape. He made it to Italy where he moved on to Oxford then the University of Ghent. Then he moved to Dublin to work at the Institute for Advanced Studies until his retirement in 1955. During his life, he became very involved in theoretical physics (specific heats of solids, with problems of thermodynamics, and the atomic spectra) he also studied the physiological studies of colour. He also studied unifying gravitation and electromagnetism. Schrödinger’s big accomplishment was his wave equation that looked at the atomic theory in a different way. He created a way to predict where electrons were in the atom. Schrödinger believed that you could never know the electrons paths in the atom because they were not definite, but he created the Schrödinger equation that can predict where the electron may be. This equation calculated the energy levels of electrons in the atom. Finally, Schrödinger received several awards that recognized his amazing accomplishments, these are the Nobel Peace Prize (1933), Max Planck Medal (1937), and the Erwin Schrödinger Prize (1956). Schrödinger sadly died in 1961 when he succumbed to a long illness.

Erwin Schrodinger was an honorable scientist who found that electrons move too fast in the atom to calculate their exact position/path. But Schrodinger still found a way, using his knowledge in mathematics, he created an equation that could predict where the electrons were. One of his most famous experiments connected to the atomic theory is Schrodinger’s cat. In this experiment he placed a cat in a box, he set up a toxic gas inside the box that would go off at a random time. Schrodinger never knew what time the gas would go off, so the cat would either be dead or alive at the time, Schrodinger would never know. He connected this to electrons, saying that he never knew where the electrons were at one given time. What Schroinger found, was that there was a cloud around the nucleus of the atom that the electrons resided in. This changed the theory of the plum pudding model(the atom having electrons, protons, and neutrons floating in a circle)set by J.J. Thomson.
Schrodinger’s atomic model had a nucleus(as discovered by Ernest Rutherford), this contained several protons and neutrons. These were all in a sort of circular shape with protons and neutrons in no specific pattern. Around the nucleus, there is a large circle, this is the electron cloud(holds all of the electrons). When creating a clear model of the atom, you would put a plus(+) in the proton particle because the charge for protons is positive, it’s charge is 1+. You would leave neutrons blank because they have a neutral charge, their charge is 0. Finally you would label electrons with a negative(-) because they have a negative charge, their charge is 1-.

Did you Know?- There are over 100 references to Schrodinger's theories in recent pop culture.

J.J. Thomson

1897 - 1940

Thomson was a prestigious scientist who was the first to discover that an atom has electrons and he used Crookes, or cathode rays, to find this information. Thomson’s research was beyond it's time because nothing like this had ever been attempted. Since nothing like this had ever been attempted everyone believed that Thomson was a maniac. Thomson born on December 18 1854 was the most daring scientists considering that he knew no one would believe his experiments were legitimate and real. Thomson did his experiments until his death in August 30 1940. He did all of his experiments in the country where he was born and died.

Did you Know?-J.J. Thomson enrolled in Trinity College at the age of only 14!

Niels Bohr

1913 - 1962

Niels Bohr was born on October 7, 1885 in Copenhagen, Denmark, he lived a full life of trial and error. Bohr had a wonderful mother named Ellen Adler Bohr who was married to Christian Bohr. His father worked as a respected professor of physiology at the University of Copenhagen. In 1912 Bohr took up a position of an assistant professor at the University of Copenhagen, that same year he married Margrethe Nørlund, after they married they had six kids. Sadly to say that two of their children died at a young age, but the rest of them became very successful with their lives. Later in Bohr’s life he earned a Nobel Prize in physics in the year 1922. In 1913 he based his thinking of the atomic structure around the studies of Rutherford’s theories. In 1921 he founded the Institute of Theoretical Physics in Copenhagen, where he was the director for the rest of his life. After that, World War 2 came into play, Bohr got kicked out because of his Jewish ancestry. After he got kicked out of Germany he went to London and got involved for a time Project "Tube Alloys", the code-name for the British nuclear weapon program, and the search for a viable nuclear fission bomb. When he got involved with that he went all over and helped with a lot more things. After World War 2 ended he went back to Copenhagen, then when he arrived he got awarded the Order of the Elephant by the Danish Government in 1947. Not many years after Bohr died in Copenhagen on November 18, 1962 at the age of 77.
Niels Bohr is a great scientist, For the research that he made it studying Thomson's atomic model and did further think and test a whole bunch more theories and came up with what is known as the hydrogen model. His model is explained as as the theory is that the energy will transferred in precisely defined quantities. The model shows the electrons orbiting the nucleus in waves which the electrons would jump from one wave to the other.

The Model that Bohr created is also called the Rutherford-Bohr model, Which was introduced by Niels Bohr and Ernest Rutherford in 1913. Bohr earned a Nobel Prize is the year 1922 for physics which he studied at the university of Copenhagen.

Did you Know?-Niels played soccer and was on his college team, his brother played in the 1908 Olympics for Denmark. This is so surprising because when you think about a scientist, athletic isn't the word that comes to mind.