Science is based off of observations A Scientific Law is a summary of what is seen in observations A Scientific Theory is an explanation of why these observations are occurring Both laws and theories are tested by using them to predict what would happen in certain situations ID: 1030795
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1. Atomic Theory
2. Atomic TheoryScience is based off of observations.A Scientific Law is a summary of what is seen in observations. A Scientific Theory is an explanation of why these observations are occurring.Both laws and theories are tested by using them to predict what would happen in certain situations.
3. Atomic Theory-Explains why all matter acts as it does because it is composed of tiny particles called atoms, the basic building blocks of all matterFirst theorized by Democritus ~400 BC in ancient Greece.He thought that matter could NOT be divided infinitely. You had to reach a smallest possible piece. He named this piece an atom, which meant indivisible or can’t be cut.
4. More DemocritusHe and his followers, atomists, said atoms were small hard particles all made of the same material, but different sizes and shapes. They were also always moving and capable of joining together.Since this was ancient Greece, He and the atomists had no way of ever proving his theories and few people believed it.
5. Law of definite proportionsAll pure compounds have exactly the same proportions by mass of elements regardless of sizeWater is always 2 hydrogen atoms to every 1 oxygen atomBy mass that is 2 (g) H : 16 (g) O
6. Law of multiple proportionsThe same elements may combine to form several different compoundsFor example H and O can combine form H2O (water) and H2O2 (hydrogen peroxide) C H and O may form alcohol, formaldehyde, ether (starting fluid) or many other things.basically if you see a couple of elements don’t assume they can only go together one way.
7. Law of conservation of mass~ mass is neither created nor destroyed in a reaction.The mass of the products must equal the mass of the reactants.
8. Dalton’s Model (1803)people started to accept the idea of atoms because of his experimentsHe worked with gases and found that they acted as though they were made of solid microscopic particlesall elements are made of atoms (indivisible and indestructible)atoms of the same element are exactly alikeatoms of different elements are differentcompounds are formed by joining two or more atoms
9. John Dalton
10. Thomson’s Model (1897) found negative particles could come from neutral elementsatom is made of smaller things (+ & -), and is divisiblesuccessfully separated negative particles (electrons) but could not separate the positive particle (protons)“plum pudding model” negative particles floating in a positively charged gel like material
11. Plum Pudding Model- ThomsonPositive GelNegativeParticles
12. Thomson’s Cathode Ray
13. Sir J. J. ThomsonThe sir meanshe was knighted
14. Rutherford’s Model (1911) fired protons at a sheet of gold foil most went through unaffected, some bounced awaythere is a small dense area of positive particles at the center of the atom- the nucleuselectrons are scattered near the outside of the atom with mostly empty space between the nucleus and the electrons
15. Gold Foil ExperimentRadioactive sourceGold foil
16. Rutherford’s Modelnucleus(small dense positive area)electronsEmpty Space
17. Ernest Rutherford
18. Bohr Model (1913) electrons move in definite orbits around the nucleus these orbits or energy levels are located at certain distances from the nucleus
19. Bohr’s ModelnucleusElectrons
20. Neils Bohr
21. Wave Model (present day) based on complex math equationsorbits are more complex than originally thoughtde Broglie stated that electrons (particles) have wave properties, and he viewed these as standing waves, like those produce when a guitar string is plucked (classical physics.)Schrodinger assumed that the electron in Hydrogen behaves as a standing wave.
22. Wave Model (continued)When Schrodinger’s equation is analyzed, many solutions are found. Each solution represents an atomic orbital.An atomic orbital is the most probable location for finding an electron.
23. What is an orbital?It is not a Bohr orbit (not moving in a circular path) How is the electron moving?We don’t know! There is a fundamental limitation to just how precisely we can know both the position and momentum of a particle at a given time
24. This is kind of how we assume an electron travelse-
25. Heisenberg Uncertainty PrincipleThe more accurately we know the particle’s position, the less accurately we can know its momentum and vice versa. We can’t know the exact motion of the electron around the nucleus. The area that an electron orbits is called an “electron cloud”
26. Louis de Broglie Erwin Schrodinger
27. Werner Heisenberg