Chemistry 121, Week 2 Notes,
Chemistry 121, Week 2 Notes, CHEM121A
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This 5 page Class Notes was uploaded by Lindsey Notetaker on Monday September 12, 2016. The Class Notes belongs to CHEM121A at University of Nevada - Las Vegas taught by Dr. Berg in Fall 2016. Since its upload, it has received 98 views. For similar materials see General Chemistry 1 in Chemistry at University of Nevada - Las Vegas.
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Date Created: 09/12/16
Introduction to Chemistry I-Week 2 Notes (September 5, 2016) Chapter 1: Matter and Measurements Chapter 2: Atoms, Molecules, and Ions Key to my notes: all notes that are taken from the lecture will be the first section, notes I take from the textbook will be the second section, and the vocabulary words from the chapter with definitions will be the last sections! (: Lecture Notes Chapter 1: Matter and Measurements Need to know about the acceptable range of data Read 1 digit after the calibration number Record ALL significant figures o Rules for Significant Figures All non zero digits are significant Zeros between two significant figures are themselves significant Zeros at the beginning of a number are never significant Zeros at the end of a number are significant if a decimal point is present Bar over any zero means that it counts as being significant o Write in scientific notation to cleanly show significant figures When doing conversions, the units should cancel out so that you are only left with what you are trying to find Density can be used as a conversion factor Chapter 2: Atoms, Molecules, and Ions Antoine Lavoisier is the father of modern chemistry o He was killed by guillotine With atoms mass is never destroyed Percentages are not changed but the amount of mass does when looking at different size samples of the same compound Different mass ratios should be recorded as integers between atoms in a compound Atoms are the fundamental building block of matter o Dalton in 1808 published “A New System of Chemical Philosophy” which contained his model an atomic theory Said that all matter consists of atoms and cannot be broken Now know that atoms that atoms be broken down into subparticles Atoms are permanent and cannot be changed Now know that with nuclear reactions it can cause elements to be changed Atoms of the same element are identical Introduction to Chemistry I-Week 2 Notes (September 5, 2016) Now know that isotopes exist which are atoms of elements with different masses Compounds have specific ratio Few compounds have slight variations of their ratios Ratios always whole numbers when compared to other atoms JJ Thomson measured the charge to mass electron “Millikan oil drop experiment” o Robert Millikan in 1909 determined the size of the charge on an electron o 1 of top 10 science experiments o Figured out the mass of an electron Plum pudding vs. raisin muffin o The debate as how the atom is made up Science discoveries often found by accident Rutherford found 3 different types of radiation o Alpha are positive charged particles Known now as helium nucleus Protons o Beta are negative charged particles Known as electrons o Gamma are neutrally charged particles Known as electromagnetic waves Neutrons Gold foil experiment by Rutherford o Proved there was a nucleus o 50 years later show electrons were made up of quarks Do not need to know what that is for this class (: o Most of the nucleus is 1000 of whole atom Holds most of the mass though of the atom Henry Moseley discovered the atomic number of elements but sadly died in World War I. o After that Britain made all scientists exempt from the draft Dalton is AMU which is the unit of atomic masses because they are so small There is always some uncertainty with numbers o Uncertainty: value but range is where the definite value is o Range = value +/ absolute uncertainty o Fractional uncertainty= (absolute uncertainty)/(value) Textbook Notes John Dalton (17661844) came up with the atomic theory o Each element is composed of extremely small particles called atoms Introduction to Chemistry I-Week 2 Notes (September 5, 2016) o All atoms of a given element are identical, but atoms of different elements are different from the atoms of all other elements o Atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions o Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kinds of elements JJ Thomson (18561940) discovered the electron through cathode rays o Also found the charge to mass ratio Robert Millikan (18681953) found charge of electron Henri Becquerel (18520 1908) discovered radioactivity Ernest Rutherford (18711937) discovered three types of radiation o Alphapositive charged particles Protons discovered in 1919 o Betanegative charged, high speed particles Electrons It takes 1,837 electrons to make the mass of a proton or neutron o Gammaneutral charged, no mass particles Neutrons discovered in 1932 by James Chadwick (18911972) The plum pudding model of an atom was that an atom was a huge uniform sphere of positively charged and there were negative electrons spread throughout o Rutherford and Marsden disproved this Most important tool for chemist is the periodic table Most molecular substances encounter contain only nonmetals Molecular formula and empirical formula are NOT always the same Metals tend to lose electrons to form cations as nonmetals tend to gain an electron forming anions Ionic compounds tend to be composed of metals bonded with nonmetals elements want to have the same number of electrons as the noble gases Vocabulary Words Atom: the smallest representative particle of an element Subatomic Particles: particles such as protons, neutrons, and electrons that are smaller than an atom Cathode Rays: streams of electrons that are produced when a high voltage is applied to electrodes in an evacuated tube Electron: a negatively charged subatomic particle found outside the atomic nucleus; it is part of all atoms. An electron mass 1/1,837 times that of a proton Introduction to Chemistry I-Week 2 Notes (September 5, 2016) Radioactivity: the spontaneous disintegration of an unstable atomic nucleus with accompanying emission of radiation Nuclear Model: model of the atom with a nucleus containing protons and neutrons and with electrons in the space outside the nucleus Nucleus: the very small, very dense, positively charged portion of an atom; it is comprised of protons and neutrons Neutrons: an electrically neutral particle found in the nucleus of an atom; it has approximately the same mass as a proton Proton: a positively charged subatomic particle found in the nucleus of an atom Electronic Charge: the negative charge carried by an electron; it has a magnitude of 1.602 X 10^19 C Angstrom: a common nonSI unit of length, denoted Å, that is used to measure atomic dimensions. 1 Å=10^10 meters Atomic Mass Unit(amu): a unit based on the value of exactly 12 amu for the mass of the isotope of carbon that has six protons and six neutrons in the nucleus Atomic Number: the number of protons in the nucleus of an atom of an element Atomic Weight: the average mass of the atoms of an element in atomic mass units (amu); it is numerically equally to the mass in grams of one mole of the element Mass Number: the sum of the number of protons and neutrons in the nucleus of a particular atom Isotope: atoms of the same element containing different number of neutrons and therefore having different masses Mass Spectrometer: an instrument used to measure the precise masses and relative amounts of atomic and molecular ions Periodic Table: the arrangement of elements in order of increasing atomic number, with elements having similar properties placed in vertical columns Period: the row of elements that lie in a horizontal row on the periodic table Group: elements that are in the same column of the periodic table; elements within the same group or family exhibit similarities in their chemical formula Metallic Elements (metals): elements that are usually solids at room temperature, exhibits high electrical and heat conductivity, and appear lustrous. Most of the elements on the periodic table are metals Nonmetallic Elements (nonmetals): elements in the upper right corner of the periodic table; nonmetals differ from metals in their physical and chemical properties Introduction to Chemistry I-Week 2 Notes (September 5, 2016) Metalloids: elements that lie along the diagonal line separating the metals from the nonmetals in the periodic table; properties of metalloids are intermediate between those of metal and nonmetals Chemical Formula: a notation that uses chemical symbols with numerical subscripts to convey the relative proportions of atoms of the different elements in a substance Diatomic Molecule: a molecule composed of only two atoms Molecular Compound: a compound that consists of molecules Molecular Formula: a chemical formula that indicates the actual number of atoms of each element in one molecule of a substance Empirical Formula: a chemical formula that shows the kinds of atoms and their relative numbers in a substance in the smallest possible wholenumber ratios Structural Formula: a formula that shows not only number and kinds of atoms in the molecules but also the arrangement (connections) of the atoms Ion: electrically charged atom or group of atoms (polyatomic ion); ions can be positively or negatively charged, depending whether electrons are lost (positive) or gained (negative) by the atom Cation: a positively charged ion Anion: a negatively charged ion Polyatomic Ion: an electrically charged group f two or more atoms Ionic Compound: a compound composed of cations and anions
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