1/19/16 Pg 2 7 Dead Dudes of Atomic Theory P1 (Pg 3) AT/ATOMS ToC (pgs 1/2) IN ?: How or why are things/new concepts discovered? Atoms & The 7 Dead Dudes of Atomic Theory any of several theories proposing that matter is composed of atoms
What is atomic theory? any of several theories proposing that matter is composed of atoms atoms: smallest particle of matter than can build to create objects around you Ancient Greece: nothing to do!
If atoms are so small, how were they discovered?! Ancient Greece: nothing to do! Around 440 B.C., Greek dude/philosopher Democritus was eating grapes & a coin 1 day Wondered what was IN the coin
No experimental data to support his idea Based on careful thinking & reasoning Said you could only cut the coin to a certain point, its smallest piece
Called the atomic hypothesis Said that smallest part was uncuttable Called it an atom Atomos- indivisible Between atoms, there lies empty space
Are indestructible Atoms have always been, and always will be, in motion There are an infinite number of atoms, and kinds of atoms, which differ in shape and size.
- mimic their material sweet things are made of smooth atoms, bitter things are made of sharp atoms, etc. How was atomic theory advanced?
John Dalton was a British chemist & teacher Stated his theory in 1803 Agreed w/Democritus: elements (stuff) are made of tiny particles called atoms Arent different shapes, though! All little spheres! Heavier material = bigger atom
Dalton vs Democritus Atoms of a given element are different from those of any other element due to their mass/size Heavier material = bigger atom All atoms of a given element are
identical All gold atoms look the same Group together = bar of gold Called Law of Multiple Proportions Build compounds
Why does different size matter? Atoms of different elements combine in a specific ratio (ie: water = H2O) based on mass Called Law of Multiple Proportions Build compounds Atoms cant be created, divided into smaller parts, or destroyed; they just rearrange themselves to make new stuff OUT ?: {DONT COPY} Pick a school appropriate material. {COPY} Draw what Democritus would believe the atom of that material would look like. Make a Venn diagram of Democritus & Daltons theories.
1/20/16 Pg 4 IN ?: Make a Venn diagram of Democritus & Daltons theories. 7 Dead Dudes of Atomic Theory Pt 2 (Pg 5) When was the next change made to the
A.T.? 1897, JJ Thomson discovered smaller particles in the atom Proved atoms could be divided, or broken down Used a cathode ray tube & found a positively charged plate attracted a beam of electricity Decided something NEGATIVE had to be in atom to be attract to the + plate What did he call his discovery?
Called the negative particles corpuscles Now called electrons Where were the negative particles in the atom? Said they were evenly spread out in the positive atom, & that all atoms had the same # Called plum-pudding model What would we possibly call this model today
What would we possibly call this model today? Provide evidence to support your choice. Record your answer on your notes page. Why do you think the next scientist disagreed with this model? Discuss & answer on notes page. Why was Thomsons theory changed?
Had research students; former student from New Zealand discovered a new structure to the atom Ernest Rutherford, 1911 How did Rutherford make his discovery?
Gold foil experiment Shot a + beam of alpha sheet of gold foil Beam was turned around in various ways & some deflected (90o) by gold foil MOST particles went THRU the gold foil Mostly empty space Tiny, dense nucleus What changes did his experimental results lead to?
stated there must be a + core to the atom Tiny, very dense center called the nucleus Most of mass of atom is here 100,000x smaller than whole atom Core contained + particles called Protons Agreed w/Thomson that electrons were evenly dispersed around outside of atom How long before the next discovery/change to theory?
1913, Niels Bohr stated the atom had a certain structure outside of nucleus Electrons were located in specific paths, or rings Also known as ORBITals Called the planetary model Are all the electron rings the same?
Each ring held a certain amount of NRG/electrons 2/8/18 Move away from nucleus = higher level = lower NRG e- strongest closest to nucleus **What other concept have we learned that this idea is similar to? (answer on note page) e- could move from level to level Gain or release NRG when they move from level to level Form of light (PHOTONS) OUT ?: How was Thomsons model different from Democritus original definition of an atom? 1/21/16 Pg 6 7 Dead Dudes of Atomic Theory Pt 3 (Pg 7) IN
1/21/16 Pg 6 7 Dead Dudes of Atomic Theory Pt 3 (Pg 7) IN ?: Use the pink IQ provided. Do we still think atoms look like the planets?
Erwin Schrodinger 1926, stated that electrons were in certain levels, but more like a cloud vs. a set ring/path Cant really locate WHERE electrons any given time Created a mathematical probability of electron location Not last model, but still considered CURRENT MODEL Areas surrounding the nucleus are like levels of atmoshpere clouds
What does the current atomic model look like? Areas surrounding the nucleus are like levels of atmoshpere clouds What issue is caused by the nucleus ONLY containing protons? Why didnt the + nucleus particles REPEL & explode?
James Chadwick; 1932 proved the existence of the 3rd particle inside atoms called neutrons Whats the purpose of this 3rd particle? binding in the nucleus
neutral, or no charge creates the STRONG force/glue keep the protons from repelling each other & exploding nucleus neutrons + + + + protons Notice the neutrons & protons are about the same size! Where are the neutrons located in Chadwicksmodel?
Adding to Rutherfords nucleus No charge, so nucleus is still + from protons What does the nucleus look like? Use the pink OQ provided.
OUT ?: Use the pink OQ provided.