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Welcome to PAP Chemistry! Tear the exit ticket paper in half. How many protons, neutrons, and electrons are in the following? Turn in to Ms. B How will 2nd period succeed in Unit 3? Pay attention in class Turn in homework Study – PPTs (papchemistry.weebly.com), videos online How will 3rd period succeed in Unit 3? Study (look over notes, flashcards) Pay attention in class Tutoring Videos online (Bozenmann science, Crash Course Chemistry, Khan Academy, Brain Pop) Take notes How will 4th period succeed in Unit 3? Study (reviewing notes, looking at feedback) Take notes Do homework Tutoring Participation How will 5th period succeed in Unit 3? Pay attention in class Take notes Do homework on time Turn in work Ask questions, go to tutoring Don’t interrupt class Papchemistry.weebly.com How will 6th period succeed in Unit 3? Take notes Study (reviewing notes, watch crash course chemistry, bozemann science videos) Class discussions Turn in homework Unit 3: Atomic Theory What is atomic theory?? The idea that matter is made up of atoms, the smallest pieces of matter. Democritus 460-370 B.C. Proposed world is empty space through which atoms move Explained why changes in matter were possible the atoms were being rearranged Lavoisier 18th century Proposed law of conservation of mass/matter Observed massreactants = massproducts 2.00 g of hydrogen + 16.00 g of oxygen = 18.00 g of water Proust 1871-1922 Proposed law of definite proportions for compounds Ex. Water is always 11% hydrogen and 89% oxygen (by mass) Atomic History Gallery Walk Time: 15 minutes Stations: Dalton (father of atomic theory) J.J. Thomson Chadwick Rutherford Bohr Structure of the Atom Scientist Years Theory Democritus 460-370 B.C. Proposed idea of atomos n/a Lavoisier 18th century Law of conservation of matter n/a 18711922 Law of definite proportions n/a Dalton 17661844 Four postulates: 1) elements are made up of atoms 2) elements are the same if they have the same atoms 3) elements are n/a different if they have different atoms 4) atoms form compounds in specific ratios J.J. Thomson* Late 1800s Plum pudding model, discovered electrons Cathode ray tube Rutherford 18711937 Discovered that atoms are mainly empty space and that mass is concentrated in a positively charge nucleus Gold foil experiment Chadwick 1932 Discovered the neutron Various Niels Bohr Early 1900s Bohr model with energy levels occupied by electrons, energy is quantized n/a Proust Experiment Thomson’s Experiment Voltage source - + Thomson’s Experiment Voltage source + By adding an electric field, he found that the moving pieces were negatively charged Able to calculate mass to charge ratio Millikan’s Oil Drop Experiment - + - + -Measure the drop and find volume from 4/3πr3 Find mass from M = D x V -From the mass of the drop and the charge on the plates, he calculated the charge on an electron Rutherford Gold Foil Experiment What he expected Because he thought the mass was evenly distributed in the atom What he got Model Over Time Bohr’s Atom •electron paths Bohr Analogy A turtle sitting on a ramp can have any height above the ground- and so, any potential energy A turtle sitting on a staircase can take on only certain discrete energies energy is released when the turtle moves down the steps (emission) only discrete amounts of energy are absorbed or released (energy is said to be quantized) Modern View Atom is mostly empty space Two regions Nucleus contains protons and neutrons Electron cloud – region where you have a chance of finding an electron Atomic Structure: Atoms contain three subatomic particles… 1. Protons…large, positive charge +1 These are located in 2. Neutrons…large, no charge 0 NUCLEUS! 3. Electrons…*tiny, negative charge -1 Electrons surround the nucleus in orbitals Reading the Squares: 1st letter Capitalized 2nd letter Lowercase Gold - Au Iodine - I Helium - He ATOMIC NUMBER (number of protons) ATOMIC SYMBOL 6 C 12.011 Carbon ATOMIC MASS (mass number = protons plus neutrons) What about neutrons? Nucleus = mass of atom = protons + neutrons Proton mass = 1 amu Neutron mass = 1 amu Boron – Atomic Number is 5. Protons = 5 Mass = 11 Mass = Protons + Neutrons How many Neutrons are in a Boron Atom? 6 Mass Number (NOT on the Periodic Table) Mass number = the sum of the protons and neutrons Number of neutrons in an element can vary (called isotopes: atoms of the same element that have different mass numbers) This means the number of _protons_ is the same, and the number of _neutrons_ is different. How to write isotopes 2 methods Method 1: Hyphen-notation method The symbol is written, then hyphen, then mass #. U-235. table) Mass # = 235. Atomic # = 92 (from periodic Method 2: Subscript Superscript Mass number → Atomic number → A X Z 23 Na 11 Isotopes of one element Isotope Name #P #N # e- Mass # Protium 1 0 1 1 Deuterium 1 1 1 2 Tritium 1 2 1 3 Notice the # Protons and # electrons is always the same since these are all hydrogen. Exit Ticket Answer the following questions using the picture to the right 1. 2. 3. 4. 5. How many protons does carbon have? How many electrons does carbon have? What is the atomic mass of carbon? What is the mass number of carbon shown above? How many neutrons does carbon have? Show how you determined this.