History of the Atom

John Dalton

Oct 2, 1803

In 1803, John Dalton discovered that small solid masses in motion. Also that he proposed the atomic theory with spherical solid atoms that were based on properties of mass. John Dalton was the first scientist to discover the atom. He inferred that atoms were smooth, hard balls, that couldn’t be broken. He also realized that atom can’t be created or destroyed. Something that is like his model that you can compare it to is a bowling ball.

J.J. Thomson

Oct 2, 1897

In 1897, J.J. Thomson discovered that an atom had electrons scattered throughout a ball of positive charge. The experiment the J.J. Thomson did was that he demonstrated that cathode rays could be deflected by a magnetic field and that their negative charge was not a separate miracle. Something that is like his model that you can compare it to is a chocolate chip cookie or watermelon.

Marie Curie

Oct 2, 1898

In 1898, Marie Curie discovered two new elements called polonium and radium, which founded a new scientific field called radioactivity. To discover polonium Marie Curie stated that the method they used was a new one for chemical research that was based on radioactivity. In 1903 Marie Curie was awarded half the Nobel Prize in Physics, for her research on the radiation miracles. She only got half of the Nobel Prize, because she shared it with her husband Pierre Curie.

Ernest Rutherford

Oct 2, 1911

In 1911, Ernest Rutherford discovered that an atom’s positive charge must be packed within a small region in its center called the nucleus. His experiment that he did to find out this information was that he aimed a beam of positively charged particles at a thin sheet of gold foil. This experiment is one of the most popular that happened with the atomic theory. An important word that he said was positive charge, because in the foil there was a positive charge in the middle of it.

Neils Bohr

Oct 2, 1913

In 1913, Neils Bohr discovered that the electrons are found only in specific orbits around the nucleus. His experiment that he did to find this out was that the planets orbit the sun in a certain way, so he inferred. Another item that he found out was that each possible electron orbit in his model has a fixed energy. His model is the nucleus in the middle then shells, energy levels and electrons were orbiting around it.

James Chadwick

Oct 2, 1932

In 1932, James Chadwick discovered many other particles that are in the atom. Before he discovered this we still believed that the atom was made up of a positively charged nucleus that was surrounded by negatively charged electrons. James Chadwick even got a Nobel Prize in Physics in the year of 1932. He figured out this discovery by putting a whole bunch of beryllium atoms with alpha particles. The answer that he found was an unknown radiation. This particle then became the neutron.

Citations

Oct 2, 1944

Citations:
1. Science Book Pages 91-93
2. http://atomictimeline.net/index.php
3. https://www.iupac.org/publications/ci/2011/3301/5_adloff.html
4. http://www.planet-science.com/categories/over-11s/science-celebrities/2010/09/marie-curie-(1866-%E2%80%93-1934).aspx
5. http://www.abcte.org/files/previews/chemistry/s1_p6.html