Ms. Mikus Tuesday, September 8, 2009

D ALTON B IOGRAPHICAL I NFORMATION John Dalton was born on September 6, 1766 and died on July 27,1844. He worked as a chemist, physicist, and meteorologist in England. He was the son of a Quaker weaver just outside of Cumberland, England. He was appointed to teacher of mathematics and natural philosophy at the New College in Manchester in He retired from this position in 1800 due to the financial constraints of the college and became a private tutor. Dalton had deuteroanopia (or color blindness) so this was often a subject he studied. Dalton also performed work on atomic theory, gas laws, and atomic weights. Dalton suffered from a minor stroke in 1837 and 1838 leaving him with a speech impediment. He was still able to perform his experiments but after suffering from several more strokes he died in 1844.

D ALTON A TOMIC T HEORY  Elements are made of tiny particles called atoms.  All atoms of a given element are identical  The atoms of a given element are different from those of any other element; atoms of different elements can be distinguished from one another by their respective relative weights.  Atoms of one element can combine with atoms of other elements to form chemical compounds.  Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process.

R UTHERFORD B IOGRAPHICAL I NFORMATION Rutherford was born in Brightwater, New Zealand on August 30, He died on October 19, 1937 in Cambridge, England. He worked in the fields of chemistry and physics. He is considered the father of nuclear physics. He was awarded the Nobel Prize in Chemistry in Rutherford received his bachelors and masters degrees from Canterbury University and then continued his studies at Cavendish Laboratory at the University of Cambridge. He was knighted in 1914.

R UTHERFORD A TOMIC T HEORY Rutherford’s contributions to atomic theory include his gold foil experiment. In this experiment he worked to prove the existence of charges in each atom is different. In the gold foil experiment he set a beam of alpha particles into a thin sheet of gold foil. Zinc sulfide surrounded the gold foil (except where the beam came through). The zinc sulfide lights up when it is struck by the beam (so he could tell were the particles were hitting). The results of his experiment was that the particles hit everywhere on the zinc sulfide. He proved that there was a centralized charge (later called the nucleus). Although he could not prove if the charge was positive or negative.

T HOMSON B IOGRAPHICAL I NFORMATION J.J. Thomson was born in 1856 in Cheetham Hill, Manchester in England. His father died when he was only sixteen years old. He studied engineering at the University of Manchester. He became a professor of physics in He was awarded the Nobel Prize in Physics in He is recognized for his work in discovering the electron, isotopes and mass spectrometry. He is credited for discovering that Hydrogen only has one electron and the natural radioactivity of Potassium. Rutherford was one of his students at Cambridge. He died on August 30, 1940 in Cambridge.

T HOMSON A TOMIC T HEORY Thomson is credited for discovering the electron in He was unsure about how it fit into the atom though. So he developed the plum-pudding model (shown to the left). In this model he hypothesized that the electrons were the negatively charged “plums” in a sea of positively charged “pudding”. He pictured that both positively and negatively charged particles were contained in the nucleus of the atom.

B OHR B IOGRAPHICAL I NFORMATION Niels Bohr was born on October 7, 1885 in Copenhagen, Denmark. He worked extensively in the field of Physics. He received the Nobel Prize in Physics in Bohr attended Copenhagen University in 1903 where he studied philosophy and mathematics. After winning awards in Physics he pursued his post-doctorate work under J.J. Thomson in Cambridge. Then he studied under Rutherford. Bohr became a professor at the University of Copenhagen. Bohr died on November 18, 1962 in Copenhagen.

B OHR A TOMIC T HEORY  First to introduce the theory that electrons travel around orbits around the positively charged nucleus (shown in the figure on the left).  Determined that the chemical properties of an atom are determined by the outermost orbit.  He found that the rotation is comparable to the earth’s rotation around the sun. Instead of gravity, electrons are pulled in to the atom by the electrostatic force.

Bohr -Biographical Information -Atomic Theory Thomson -Biographical Information -Atomic Theory Dalton -Biographical Information -Atomic Theory Rutherford -Biographical Information -Atomic Theory

C ONCLUSION Each scientist’s discoveries are interconnected. Many of them even studied under each other. Dalton started it all out by helping us to understand that each atom is different. He discovered that each atom had its own weight and properties, but he could not explain why this was the case. J.J. Thomson picked up on Dalton’s discoveries and added that each atom has electrons. He knew about this property, but he described that it was just a random mixture of positively and negatively charged particles. Rutherford picked up on Thomson’s experiments by doing his gold-foil experiments, that proved that Thomson was right about each atom having electrons. Rutherford further went to prove that instead of a random mixture it was ordered (the negatively and positively charged particles were not located in the same place). Rutherford had a hard time explaining exactly what the atom looked like, until Bohr came around (who also studied under Thomson). Bohr was able to put it all together. He took what was understood from Dalton, Thomson, and Rutherford, and developed his model, which we still use today! See this elaborate web of work in the flowchart link below.

Click here to find more information

For a big picture look at atomic theory (from 460 BC to present) visit this website: i=48muSsu6IIjosQP1wMHLCw&sa=X&oi=timeline_result&ct=title&resnum=11 &fp=b7f806229eacb72c N EAT W EBSITE

I LEARNED :  I learned how to create and use a word web.  I learned how to effectively use the hyperlink function.  I learned how this could be a good alternatively to paper writing in class (or a good lead into paper writing). It helps students organize research.  I learned how to transfer “video”-pictures from the internet  I learned to use the Microsoft website to download cool backgrounds and sounds.  The value of sharing (how this can be implemented in the classroom).