CHEM 101 1nd Edition Lecture 4 Outline of Last Lecture I. The 2 Kinds of NumbersII. Rules of Significant FiguresIII. Dimensional AnalysisOutline of Current Lecture I. RadioactivityII. About AtomsIII. IsotopesIV. Counting AtomsCurrent LectureI. Radio Activitya. Marie Curiei. Able to show that the atom was charged by deflecting a tight bean with negative and positive plates.b. Sir Joseph John Thomsoni. Is an experiment similar to Curies, he was able to determine the charge tomass ratio of an electron with a magnetic field coil perpendicular to electric field. c. Ernest Rutherfordi. Aimed alpha particle beam and aimed it at gold, and found most went straight through, but some were defected. From this he deducted:1. Atoms are mostly empty space2. The mass of an atom is located primarily in the nucleus at the center of the atom3. The charge on the nucleus is positived. Atomic Compositionsi. The atom is mostly empty space1. Protons and neutrons are in he nucleus2. The number of electrons is equal to the number of protons. 3. Electrons in space around the nucleus.4. Extremely small, One teaspoon has 3 times as many as the Atlantichas teaspoons of water.ii. ElectronsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Negative electrical charger, -12. Relative mass = .0005 atomic mass units (amu)3. Found in space around nucleusiii. Protons1. Positive electrical charge, +12. Relative mass = 1.007 amu3. Found in nucleusiv. Neutron1. No charge. 2. Relative mass = 1.009 amuII. About Atomsa. Atomic Numberi. All atoms of the same element have the same number of protons in the nucleusii. Atomic Number Z = number of protonsiii. On top of elemental symbolb. Atomic Weighti. This tell us the mass of one atom of an element relative to one atom of another elementii. On the Bottom of elemental symbolc. Mass Number, Ai. Mass Number = the number of protons + the number of neutronsIII. Isotopesa. Isotopesi. Atoms of the same element (same Z) but different mass number (A)b. Hydrogen has 3 Isotopesi.1H hydrogen1. AKA Protium2. 1 proton and 0 neutronsii.2H Dueterium (D)1. 1 proton and 1 neutroniii.3H Trutuym (T)1. 1 protons and 2 neutronsiv. Some elements have only 1 isotopec. Some isotopes are unstable i. Radioactive decay 1. Isotopes decay, loose electrons, until they reach a stable stated. Atomic Weighti. Because of the existence of isotopes, the mass of a collection of atoms has an average valueii. Average Mass = Atomic Weightiii. Boron is 19.9% 10B and 80.1% 11B1. = 0.199 (10.0 u) + 0.801 (11.0u) = 10.8 uIV. Counting Atomsa. Atoms are very small, difficult to weigh and countb. How do we measure them accuratelyi. We need a number that describes a larger number of atomsii. Can think of it like dozen or tonc. In chemistry we use the term molei. A mole (mol) is 6.02 x 1023 somethingii. 1 mole is the amount of substance that contains as many particles as there are in 12.0 g of 12Cd. We get this fromi. Avogadro's Numberii. 6.02214199 x 1023iii. It all depends on how big the atom
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