Greek Philosophers
Democritus was one of the earliest scientists to study the atom. He stated that all matter came from small, indestructible balls. Although he believed that atoms are too small to be seen by the human eye, he also believed that atoms were solid. He didn't know of or believe that each atoms has protons, neutrons, and electrons. The atoms that he believed in were different in size, shape, and color depending on which element the atom is made up of. He published his theory in 465 B.C. His theory also stated that solids are made of small, pointy atoms liquids are made of large, round atoms, and oils are made of very fine, small atoms that easily slip past each other.
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Dalton
John Dalton was born September 6, 1766. He was an English chemist. Many people had forgotten about the study of atoms over the course of time. He composed many experiments that lead him to believe that atoms actually exist. His theory is called Dalton's Atomic Theory. He believed that atoms are indestructible and invisible to the human eye. Dalton developed the concept of a compound, which is a mixture of two or more elements.
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J.J. Thomson
On December 18, 1856, J.J. Thomson was born in Manchester, England. He began to study the atom thoroughly in 1897. In his studies, he provided the idea that atoms are made up of even smaller particles. He also proved that atoms are divisible. His theory was called Thomson's Model. His theory stated that atoms are made up of positive and negative charges. He believed that negative particles were spread throughout the atom while the positive charge remained in the empty space.
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Rutherford
On August 30, 1871, Ernest Rutherford was born in Brightwater, New Zealand. His model is called Rutherford's model. During his studies, Rutherford discovered the nucleus. He believed that this nucleus was in the center of the atom. He also discovered protons. After he discovered this, he found that they were located in the nucleus and that electrons are outside of the nucleus.
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Modern Atomic Model
The modern atomic model is called the electron cloud model. It was created by Erwin Schrödinger in 1925. I contains a small nucleus at the center. Inside the nucleus, is an equal amount of protons and neutrons. Electrons are supposedly scattered outside of the nucleus in random order. The atom is considered neutral due to the amount of equal positive, negative, and neutral charges within.
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Periodic Table of Elements
*Many elements on the Periodic Table of Elements were used in early civilizations as weapons, jewelry, etc.
*12 known elements before 1700s.
*79 known elements in the early 1900s.
*118 known elements today.
*Mendeleev introduced a table that increased by atomic mass
*Moseley found elements that were out of order in Mendeleev's table.
*Moseley introduced a table that increased by atomic number instead of atomic mass.
*The modern Periodic Table of Elements has groups that represent columns and periods that represent rows.
*It is split into representative and transitional groups.
*Includes metals, nonmetals, and metalloids.
*Elements are either solids, liquids, or gases at room temperature.
*Includes synthetic elements (artificial elements that do not naturally occur on earth).
*12 known elements before 1700s.
*79 known elements in the early 1900s.
*118 known elements today.
*Mendeleev introduced a table that increased by atomic mass
*Moseley found elements that were out of order in Mendeleev's table.
*Moseley introduced a table that increased by atomic number instead of atomic mass.
*The modern Periodic Table of Elements has groups that represent columns and periods that represent rows.
*It is split into representative and transitional groups.
*Includes metals, nonmetals, and metalloids.
*Elements are either solids, liquids, or gases at room temperature.
*Includes synthetic elements (artificial elements that do not naturally occur on earth).