A. Debating the Nature of Matter
1)
There were many ideas of which one of the classical elements was the key element: Earth, Air, or Fire?
- Xenophanes (Earth) – Xenophanes believed that the whole existence of the universe and everything else within it was created from something. He believed nothing could have ever existed without this element. Nature, he thought, was incapable of changing (making it become non-existence). He believed this because Nature was here from the start and will always continue to be a present element.
- Anaximenes (Air) – Anaximenes believed air exists at different degrees of density. Under the influence of cold or heat, air can rise to many different phases of existence. Hot and cold, rarefaction and condensation are the two different directions air can go. He believed condensation has the result of stone, while rarefaction has the result of fire.
- Heraclitus (Fire) – Perpetual change is what fire symbolizes. It changes one substance into another without itself changing. This is the reason Heraclitus believed fire is the origin of all matter.
www.friesian/elements.htm
http://paganwiccan.about.com/od/wiccaandpaganismbasics/a/elements.htm
http://www.economicexpert.com/a/Classical:element.html
http://www.ics.forth.gr/~vsiris/ancient_greeks/presocratics.html http://www.utm.edu/research/iep/x/x-phanes.htm
http://www.thebigview.com/greeks/heraclitus.html
http://www.utm.edu/research/iep/a/anaximen.htm
2)
The science with the goal of achieving ultimate wisdom is called Alchemy. The alchemist had three main ideas. They wanted to find a mixture or notion to pro-long life or “live forever.” Secondly, they wanted to find the appropriate combination of ingredients to cure all diseases and illnesses. To turn base metals, such as lead into gold, was the alchemists’ final goal.
http://dept.physics.upenn.edu/courses/gladney/mathphys/subsection1_1_3.html
3)
- Laws of Conservation of Mass
1) No change in the quality of matter during a chemical change – the matter does not change when a chemical change occurs
2) Matter is never created or destroyed – matter will always be present, no matter what happens
3) The mass of products is always equal to the mass or reactants – the mass of the substances produced by a chemical reaction, is always equal to the mass of the reacting substances
- Law of Definite Proportions
1) A chemical compound always contains the same elements in the same proportions by weight – the weight of an element is always the same, no matter how much of it you have
- Law of Multiple Proportions
1) The mass of one element combined with the mass of a second element are equal – the elements are together now, so splitting them would cause the same amount of mass to go to each side
http://chemistry.about.com/library/weekly/aa012903a.htm
http://www.britannica.com/EBchecked/topic/397165/law-of-multiple-proportions
http://www.thefreedictionary.com/law+of+definite+proportions
http://www.mi.mun.ca/users/edurnfor/1100/atomic%20structure/tsld004.htm
http://www.cartage.org.lb/en/themes/Sciences/Chemistry/Generalchemistry/Energy/LawofConservation/LawofConservation.htm
4)
John Dalton’s Modern Atomic Theory:
1) All matter consists of tiny particles.
2) Atoms are indestructible and unchangeable.
3) Elements are characterized by the mass of their atoms.
4) When elements react, their atoms combine in simple, whole-number ratios.
5) When elements react, their atoms sometimes combine in more than one simple, whole-number ratio.
http://antoine.frostburg.edu/chem/senese/101/atoms/dalton-postulates.shtml
5)
Alchemists followed the doctrine of Aristotle, Plato, and Empedocles. Empedocles believed all matter consisted of four elements: Earth, water, air, and fire. Aristotle believed in a fifth element, ether, which was a substance that could prolong life. They believed that there were no atoms that made up matter. All of these elements created everything else in existence. They believed that if they found the elixir, life would be perfect. Alchemists today use Aristotle’s fifth element as a goal for theirs to achieve.
Leucippus and Democritus, the original atomic theorists, had exactly the same ideas. Both state that atoms are an extremely small particle, making up the nature of everything. Those atoms contain no empty space and are completely filled. Atoms are indivisible physically but not geometrically, and are indestructible (eternal). Both believe in atoms with distinct shapes and sizes, and that all atoms are in constant motion.
John Dalton’ atomic theory is based mostly off of Leucippus and Democritus. This is because alchemists don’t believe in atoms. Dalton’s theory agrees with many beliefs of the original atomic theorists.
http://www.cartage.org.lb/en/themes/Sciences/Chemistry/Generalchemistry/Energy/LawofConservation/LawofConservation.htm
http://www.thebigview.com/greeks/democritus.html
(The Ideas of the Greek article)
B. Discovering Subatomic Particles
6)
J. J. Thomson constructed a cathode ray tube with a metal cup and an
electrometer on one side, away from the cathode. Until the tube was
activated and the beam was magnetically deflected towards the metal
cup, it showed no charge. In Thomson's first experiment, he was able
to find that the negative charge always follows exactly the same path
as the cathode rays and was therefore a property of the cathode rays.
The second experiment was to prove if rays could be deflected by an
electric field. He made an almost perfectly vacuumed tube with
phosphorescent paint on one end. Thomson found that in his second
experiment, the rays did bend under the influence of an electric
field, but in the direction of the negative charge. The mass-to-charge
ratio was what Thomson was looking for in his third and final
experiment. He wanted to see how much the cathode rays were deflecting
by the electric field and how much energy they carried. He found that
the rays must be very light and/or very highly charged. This is
because the mass-to-charge ratio was over 1000 times lower than that
of a hydrogen ion.
In 1909, Robert Millikan wanted to find the balance between downward
gravitational pull and the upward electric and buoyant forces if
charged oil droplets suspended between two metal plates. He noticed
that when he started the electricity, some particles of the sprayed
oil started to rise, indicating the electric force was greater than
the pull of gravity. He created an equation fir the different
electricity amounts and the mass of the droplets. His equation was:
q=m•g/E or g•E=m•g
Values
E - the applied electric field
q - the charge of the droplet
m - the mass of the droplet
g - the acceleration due to gravity
In 1909, Ernest Rutherford and two scientists fired a beam of alpha
particles at a thin gold foil. He concluded that the electrons,
carrying a negative charge, would go right through the positively
charged gold foil, keeping everything electrically neutral. He stated
in his results that most of the particles did travel straight through
the foil with little or no deflection, with less than one in ten
thousand particles rebounding.
Some particles were thrown back in the same path that they came,
meaning one thing. The alpha particles must have come in contact with
massive amounts of positive charge, repelling the particles straight
back. Thomson said, "as if you fired a 15-inch shell at a piece if
tissue paper and it came back and hit you." Thomson's current bun
model of the atom, which had a positive charge spread thinly over the
entire atom, had no hope of explaining the results.
James Chadwick did an experiment with particle bombardment. He smashed
alpha-particles into the rare metallic metal beryllium, and allowed
the radiation to hit another object, paraffin wax. After the beryllium
radiation hit the hydrogen atoms in the wax, the atoms were sent to a
detection chamber. The results of the experiment showed massive
amounts of neutral particles, which Chadwick called neutrons. James
Chadwick was able to find the mass within an atoms nucleus
http://wapedia.mobi/en/J._J._Thomson
http://chemistry.about.com/od/electronicstructure/a/millikan-oil-drop-experiment.htm
http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Ryan_Mcallister/Slide3.htm
http://www.juliantrubin.com/bigten/millikanoildrop.html
http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html
http://www.light-science.com/chadwick.html
7)
| Ernest Rutherford’s Nuclear Atom | Niels Bohr’s Planetary Atom |
|    
|    
|
| - In this model, there is a nucleus (the center of an atom containing protons and neutrons) that is being surrounded by electrons. Unlike Thomson’ “Plum Pudding,” this atom has moving parts and is more accurate. | - Unlike the Nuclear Atom model, the Planetary model has a more complex system. The nucleus is now made of protons and neutrons. This is the model most representing the atom. |
| http://www.cfo.doe.gov/me70/manhattan/exploring.htm | http://abyss.uoregon.edu/~js/images/rutherford_atom.gif |
| | |
C. Formulating Quantum Mechanics
8)
Max Planck determined energy is released and absorbed by atoms in certain fixed amounts known as quanta. Radiation, such as white light, is emitted when solids are heated. Planck said that energy can be released or absorbed through atoms, but only in “chucks” of a minimum size. The name quantum, or fixed amount, was the name Planck gave to the smallest quantity of energy that can be emitter or absorbed as electromagnetic radiation. Planck also states that energy can be absorbed or emitted by matter in whole-number multiples.
Albert Einstein took Planck’s work further with the photoelectric effect. He determined that radiant energy is so quantized that he called them discrete energy packets photons. Einstein theorized that electromagnetic radiation has both wave and stream characteristics of particles. The emissions of electrons, from the surface of a metal in response to the light, is called the photoelectric effect. Einstein thought that photons interacted in the metal with the electrons like discrete particles, and not as a continuous wave. The energy of each photon remains the same (as long as the frequency of the radiation was held constant). Increasing the intensity of the radiation would cause more electrons to be ejected, but each electron would carry the average amount of energy.
Neils Bohr developed the quantized electrons. He not only helped clearing up problems with quantum physics, he developed the concept of complementarily. The concept explains that items could be separately analyzed as having several contradictory properties. Complementarily is said that single quantum mechanical entity can behave as a wave or as a particle, but never both at the same time.
Louis de Broglie asked if a stream of particles could possibly show the properties of a wavelength if the radiant energy was under the appropriate conditions. He said that the characteristics of an electron or wavelength or any particle depends on its mass and velocity. h/mv= the wavelength of an electron. When mass (m) and velocity (v) are multiplied together, it makes the particles momentum. He described the characteristics of the wave of material particles as matter waves. After publishing his theory, experiments showed the wave properties of the electron. The experiments showed that electrons diffract by crystals, showing that a stream of moving electrons shows the same wave-like behavior as electromagnetic radiation. Louis de Broglie showed that a single quantum could act as a stream but have the characteristics of a wave as well.
Werner Heisenberg tested how to calculate the exact location and momentum of an electron with wave properties. He called it the uncertainty principle. As with the electrons of an atom, it is impossible to know both the exact momentum and location of an electron in space. With experiments, they concluded that the size of an electron is so small, that it is almost impossible to find the exact location, but more of an area or region in which it can be contained.
Erwin Schrödinger posed an equation that incorporated both the wave-like and particle behavior of an electron. He was trying to find a way to deal with subatomic particles, which are known as quantum mechanics or wave mechanics. When Schrodinger was solving his equations, they became known at wave functions, which is an electrons matter wave. This helps find the electron’s location. He was able to improve Heisenberg’s principle by being able to find the probability that an electron would be found at a given location.
http://www.spaceandmotion.com/Physics-Max-Planck.htm
http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter4section4.rhtml
http://www.spaceandmotion.com/Physics-Max-Planck.htm
http://www.physlink.com/Education/askexperts/ae24.cfm
http://en.wikipedia.org/wiki/Complementarity_(physics)
D. Devising a Periodic Table of Elements
9)
There have been many attempts at the periodic table, starting as early as 1817.
Johann Dobereiner, in 1817, put his law of triads out to the public. He had two tables with three elements in each. The first table was of Alkali formers, while the second table was of salt formers. The middle element in the tables had the atomic mass about average of the other elements. This was the first time the atomic mass was used and showed any importance. de Chancourtois presented his paper titled Computes Rendus in 1862. He put the atomic weight on the outside of the cylinder. He represented an atomic weight increase of sixteen by one complete turn of his cylinder. 1864 was the year John Newland published his Law of Octaves. He also ordered the elements by atomic mass, but he found similarities within. The element being looked at was similar to the element eight places further on. His table had some problems though. In one row, he had oxygen and sulphur, along with iron, a metal. For this reason, his table wan sot accepted by other scientists.
Three major people helped discover, organize, and place elements on what we now call the periodic table. Dmitri Mendeleev was almost correct when he organized by elements with similar properties together vertically. He failed to notice organizing by atomic mass is wrong. Henry Moseley saw that organizing with the atomic number, you can solve many mistakes created by organizing with the atomic mass. Glenn Seaborg is well known for finding over 100 isotopes of elements in the periodic table.
Dmitri Mendeleev arranged the elements known at the time in order of relative atomic mass. He realized that the physicals and chemical properties of the elements were related, in a "periodical way," to their atomic mass. He also arranged them into vertical columns in his table so that groups of elements with similar properties fell together. Mendeleev also left room for elements he thought were undiscovered still, which in some cases, came out to be right.
Henry Moseley used the atomic number instead of the atomic mass for organizing his table. Mendeleev broke his own rule sometimes by using the atomic mass, but wanting an element to be in a group with similar properties. Moseley's atomic number rule solved many problems like this one
Glenn Seaborg and his colleagues are responsible for finding more than 100 isotopes of elements on the periodic table. He found the heaviest elements on the table, and named them the Actinide series. Also, for the 'created' elements, he called those the Transactinides.
Without these men and the discoveries they made, the periodic table might look very different. With organizing by similar properties and atomic number, to finding 100 isotopes of elements, they have changed the periodic table forever.
http://corrosion-doctors.org/Periodic/Periodic-Mendeleev.htm
http://corrosion-doctors.org/Periodic/Periodic-Moseley.htm
http://corrosion-doctors.org/Periodic/Periodic-Seaborg.htm
http://corrosion-doctors.org/Periodic/Periodic-Newlands.htm
http://corrosion-doctors.org/Periodic/Periodic-de-Chancourtois.htm
http://corrosion-doctors.org/Periodic/Periodic-Dobereiner.htm
Dmitri Mendeleev Original Periodic Table
