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Chemistry Notes (pg. # 1) Chemistry _ _ - Def: The study of all _________ and the ________ they can undergo. -The study of m________ and e________ The word “Chemistry” comes from the word “Alchemy”, and has its roots in this “endeavor”. Chemistry, the C________ science: -Chemistry has been called the c________ science because it o_________ so many other sciences. Ex. Biology, physics, engineering, medicine - Chemistry is considered the central science, and the idea of the _________ is central to the central science. Atomic Theory: Question: What would happen if you were able to cut a piece of aluminum foil over and over and over…Would you always still have aluminum? Democritus- G______ p_______ (450 B.C.) who proposed the idea of atoms. He called them “_______” - Democritus believed that atomos were small, i________ particles. ____________- The search for a general understanding of reality by chiefly speculative rather than observational means. - Limitation of _____________: Does not use ex____________. ____________- systematic knowledge of the physical or material world gained through observation and e_______________. Limitation of ___________: Limited to information gained through p_____________ e_____________. - The ideas of Democritus were dismissed by his fellow philosophers through the use of l_______; however, the idea of the atom was re-visited by the s_________ John Dalton in the early 1800’s. - Modern View of The Atom: The atom is composed of ________, _______, and ______. Particle: Mass: 1.0073 amu 1.0087 amu 0.0006 amu Charge: (+) Location: Question: How did scientists determine that the atom is made up of ____________, ____________, and ____________? - Also, how did they determine that there is a ____________ and an electron “__________”? Evidence for the Negative Electron: Cathode Ray T_____ Experiment: The Cathode Ray T______ experiment showed that by deflecting a stream of particles with a magnet, atoms must contain n_______ c______ p_______. - This was significant because it showed that atoms were not simply small indivisible “balls”, but rather had a s________. - From the Cathode Ray Tube Experiment came the P____ P_____ model of the Atom. (pg. # 1 continued…) Evidence For the Positive Nucleus: Rutherford’s G______ F_______ experiment: Rutherford shot (+) particles at a sheet of gold foil. Results: Most of the particles went ______ _______. Some particles deflected s_______ b______ Analysis: 1.)This showed that most of the atom is in fact e______ s_____ 2.)Also, the positive charge is very c________ in a small _________. 3.) This experiment disproved the _____ _____ ______. Chemistry Ch. 3 Notes (pg. # 2) Question: What makes one element different from another? Ex. Why is copper different than aluminum? Hint: It probably has something to do with the ______. Henry Moseley- English scientist who determined what made atoms of the various elements unique from each other. He found that each element has a unique p_______ c_______ in the nucleus, and thus a certain n_______ of ________. Atomic Number: - Atomic Number- The number of p________ in the nucleus. Elements are identified by their A_______ N_______. Ex. Indicate which element has each of the following atomic numbers: a. 34 _________ b. 12 _________ c. 7 _________ d. 6 _________ Ions: - A neutral atom has an e_______ number of protons and e_______. Ex. A neutral Li atom has ___protons and ____ electrons - An _____ is an atom (or small molecule) that has either _______ or_______ an electron or electrons. - Ions as a result have a net c________ Ex. Na (neutral) has ___ protons and ___ electrons Na+ has ____ protons and ____ electrons Ex. Determine how many protons and electrons each of the following ions have. Ca2+ Al3+ F- N3- Isotopes: Isotope- Atoms of the s_______ element with a different number of _________. Ex. Carbon-12 isotope: ____ protons, ____ neutrons Carbon-14 isotope: ____ protons, ____ neutrons Mass Number: The mass number of an isotope is the number of ________ plus the number of ________. Ex. Carbon-12 Ex. How many protons and neutrons does an Oxygen-15 atom have? Protons = _______ Neutrons = ______ Notation of Isotopes: Ex. 37 Cl Ex. How many protons and neutrons do the following isotopes of carbon have? 12 13 14 C C C Chemistry Ch. 3 Notes (pg. # 3) The Atomic Mass Unit: 1 a.m.u. is defined to be _____ the mass of a ________ isotope. - In other words, a ________ isotope has a mass of exactly ______ a.m.u. Average Atomic Mass and Relative Abundances of Isotopes: - All isotopes of an element do not have the same _______. - The Average Atomic Mass is a w_________ average of all the isotopes of an element -The average atomic mass appears on the _________ __________ of the ________. 6 C 12.011 - Certain Isotopes of an element are more s_______ than others. As a result, there is a Relative Abundance of each isotope. Relative Abundance- The percentage of an element that is composed of a certain isotope. ex. The relative abundance of 12C in carbon is 98.89%. - So, in any sample of carbon, 98.89% of the sample will be the carbon-12 isotope. (note: Notice how the average atomic mass of carbon is very close to 12 amu) Calculating Average Atomic Mass: Avg. Atomic Mass = (Mass of Isotope 1)(% abundance/100) + (Mass of Isotope 2)(% abundance/100) +… Ex. Strontium has four isotopes with the following masses: 83.913 amu (0.56%) 85.909 amu (9.86%) 86.909 amu (7.00%) 87.906 amu (82.58%) Calculate the average atomic mass of strontium.