Atomic theory. Atoms: The Building Blocks of Matter

Transcription

1 Atomic theory Atoms: The Building Blocks of Matter

2 First, there was Democritus Democritus was a Greek philosopher atomos He came up with the idea of the atom around 400BCE He had no evidence, he just thought that that was just the way the world should work

3 Aristotle Aristotle is the most famous and most influential of the Greek philosophers He thought Democritus was nuts! Too bad for Democritus And atomic theory

4 A brief history of the atom Democritus: atomos No experiments not believed Aristotle: 4 elements make up everything Earth Air Fire Water 4 th century BCE Ancient Greece

5 The word atom comes from a Greek word that means unable to be cut and you Imagine kept on cutting you the leftover had a piece of in half gold that you then cut in half Go Gold and then you cut one of these smaller pieces in half

6 The word atom comes from a Greek word that means unable to be cut and kept and going kept going An atom of gold Eventually you would have 1 piece of gold and left. kept If you cut it in half, you going wouldn t have gold any more you d have something else. This tiny, tiny single piece of gold is called an atom of gold. An atom is the smallest particle of an element that acts like the element.

7 Hundreds of years later Law of Conservation of Mass (1789) Mass is neither created nor destroyed during chemical or physical reactions. Antoine Lavoisier Total mass of reactants = Total mass of products

8 Soon after that John Dalton Atomic Theory Early 1800 s England 1. All matter is made up of tiny, indivisible particles called atoms. 2. Atoms of the same element are identical same physical and chemical properties 3. Atoms of different elements are different different physical and chemical properties 4. Atoms can chemically combine in whole number ratios to form compounds and physically mix to form mixtures. 5. An atom cannot be changed into an atom of a different element by a chemical change they may be combined, separated, or rearranged, but never created, destroyed, or changed.

9 A little after that 1897 JJ Thomson Cathode Ray Tube Discovers the electron is negative

10 And a little after that Goldstein (1886) Discovers canal rays (proton) Milliken (1909) Oil drop experiment finds the charge on an e-

11 And after all that 1911 Rutherford s Gold Foil Experiment

12 And after all that Ernest Rutherford Gold Foil Experiment Discovers the Nucleus

13 Models of the Atom Dalton Model Solid Sphere Thomson Model Blueberry Muffin blueberries = electrons cake/muffin = positive matter e- Positive material

14 Models of the atom Rutherford Model Dense, positive nucleus Electrons revolving around nucleus in circular or elliptical orbits Mostly empty space

15 Models of the atom Bohr Electrons are found in specific energy levels Like planets around the sun

16 More on Models Electron Cloud or Quantum Mechanical Model Electrons are in continuous motions and are shown as a probability cloud

17 Orbitals Orbital- the area around the nucleus in which it is most likely to find an electron. The come in a variety of shapes and sizes!!! S P D F Sphere peanut daisy/donut funkadelic

18 Orbital Shapes 1 type 3 types 5 types 7 types Check out this site for cool pics of orbitals!!!!!!!!!!

19 Starting Electron Configurations You have an address, so does an electron. Most general = energy level (1, 2, 3, etc) sub- level (s, p, d, or f) degenerate orbital Most specific = spin

20 Electron Configuration Rules The Rules Aufbau Principle- electrons fill lowest energy orbitals first. Pauli Exclusion Principle- electrons will spread out into degenerate orbitals before pairing. Hund s Rule- electrons in the same orbital will have opposite spins (one up and one down)

21 The Diagonal Rule Tells the order of the energy of the orbitals 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s

22 Configuration Diagrams An electron is represented by an arrow Only two arrows per box Place all up arrows in first Try to create some Diagrams at this Website

23 Electron Configurations These are the same as the boxes, only they take up less space Large # = energy level Letter = orbital shape superscript = how many electrons Element # 19, Potassium: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

24 Noble Gas Notation Look for the noble gas that comes before the element you are trying to describe. Write the noble gas symbol in brackets [ ] Follow the symbol with the remaining orbitals that are necessary to account for all the electrons in the desired element.

25 The Electromagnetic Spectrum Organizes light waves by energy, wavelength, and frequency

26 The photoelectric effect Photon a particle of light that contains a specific amount of energy (quantized) The photoelectric effect a photon of light hits and energizes an electron in an atom. This causes the electron to jump to a higher energy level. The electron inevitably falls back down to the lower energy level, and releases light.