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440
The Ancient Elemental Concepts
In ancient times, many believed that life was sustained by fundamental elements. The ancient Greeks believed that these elements were fire, water, air and earth. Ancient Chinese believed that the fundamental elemnts of life were metal, earth, fire, water and wood. -
440
Hypothesizing About Atoms
The first people to ever hypothesize about the atom were three well-eduacated, aristorcatic philosiphers. They were known as Leucippus, his student Democritus who is famous for creating the basic Particle Theory of Matter, and finally, Democritus' predecessor, Epicurus. Their hypothesis was based on the concept of breaking a rock into its finest bits. However, it was not popukar due to the fact that the elemental system was so deeply rooted into the Greeks' way of life. -
Period: 440 to
Development of Atomic Theory Over Time
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Antione Lavosier: Law of Conservation of Mass
It was in the year 1789 that a French scientist named Antoine Lavosier discovered the Law of Conservation of Matter. This law states that during a chemical reaction, matter is not created or destroyed. It was an important discovery because it inspired further scientific research by future generations. -
Joseph Proust: Law of Constant Composition
Joseph Proust stumbled upon something vey valuable in terms of atomic research. The French chemist founded the Law of Constant Composition wihich tells us that the elemental structure of one substance is constant regardless of how it was composed. Much like Lavosier's findings regarding atoms, Proust's newfound law prompted deeper studies of the atom in the future. -
John Dalton and the Modern Atomic Theory
John Dalton was the first to reconsider the ancient idea that different materials and elements consist of different types of atoms. Simply put, Dalton produced the Modern Atomic Theory. This theory has four principles.
1. All matter is made up of tiny and indivisible particles called atoms
2. All atoms of the same element are identical
3. Atoms of varying substances have different properties
4. Atoms of different substances can be combined to make an entirely new substance -
John Dalton and the First Periodic Table
John Dalton peiced together what is considered to be the first periodic table. However, it was nothing like what we are used to seeing today. It was a short list of substances that were thought to be elements. They were paired with symbols to help scientists communicate easily. -
Dimitri Mendeleev: Father of the Modern Periodic Table
Over the years, scientists discovered new elements, hence they also discovered new atoms as well. Before Dimitri Mendeleev created the periodic table in 1869, elements were classified by their reaction strength or atomic number. Mendeleev combined these methods to create the periodic table. He knew it was incomplete, so he left spaces for new elements, so that they may fit into the table no matter when they were found. -
J.J. Thomson
John Joseph Thomson was a British scientist who used Einstein's Theory of Relativity to discover the electron. He did this by studying the electric discharge of atoms after travelling through a cathode ray. This caused the visual model of the atom to undergo another modification. -
Theory of Relativity
In 1905, Albert Einstien suggested that atoms have energy and velocity and that this relates to its atomic weight. This laid groundwork for many other scientists. This theory is known as the Theory of Reativity. -
The Nucleus
Thomson's student, Ernest Rutherford, is credited with finding the nucleus of an atom. He did this through an experiment where particles were shot through a variety of thin foils, most notably gold. One in every eight thousand particles were deflected while the others peirced the metal. The deflected particle was extremley dense, and later classified as the nucleus. This led to another change in the atomic model. -
Bohr Model
Neils Bohr devloped the Bohr Model for the atom in 1915, based on Ernest Rutherford's work. His model demonstates the atom as if it were a part of the Solar System, where neutrons orbit the nucleus. The orbit has levels to it and is based upon three rules. First, neutrons have a unchangeable size and energy content. Second, neutron orbits are classified by energy content. Lastly, radiation is absorbed or released when neutrons change orbiting levels. -
James Chadwick and the Neutron
1932 was the year that British scientist James Chadwick made a shocking discovery. He discovered neutral particles which orbited the nucleus of an atom. These particles are called neutrons. Some find it shocking that Ernest Rutherford had not made this discovery sooner, but others argue that all comes in due time, as he also learned that adding or subtracting neutrons from an atom can render it a stable or unstable isotope. -
Quarks
Quarks are elementary particles found within protons and neutrons. They led to a distinct change in the atomic model, so that there is now a Quark Model. Quarks were discovered by Murray Gell-Mann and George Zweig in 1964 all the way to 1968. The final quark, called the top-quark was not found until 1995. -
Future?
Our understanding of the atom has come a long way since the first ideas of ancient societies, however there is still more to be unearthed. What is the future of the atom?
