Chapter 2 Notes on Atoms and Elements - Chemistry

Chemistry and Chemical Reactivity 1 6th Edition John C. Kotz Paul M. Treichel...

Chemistry and Chemical Reactivity 1 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 2 Atoms and Elements Lectures written by John Kotz ©2006 © 2006 Brooks/Cole Brooks/Cole Thomson - Thomson  ATOMS AND ELEMENTS 2 © 2006 Brooks/Cole - Thomson  3 Radioactivity One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876- 1934). She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces. © 2006 Brooks/Cole - Thomson  4 Types of Radioactive Emissions © 2006 Brooks/Cole - Thomson  5 Types of Radioactive Emissions © 2006 Brooks/Cole - Thomson  6 ATOMIC COMPOSITION Protons – + electrical charge – mass = 1.672623 x 10-24 g – relative mass = 1.007 atomic mass units (u) Electrons – negative electrical charge – relative mass = 0.0005 u Neutrons – no electrical charge – mass = 1.009 u © 2006 Brooks/Cole - Thomson  7 ATOM COMPOSITION The atom is mostly empty space protons and neutrons in the nucleus. the number of electrons is equal to the number of protons. electrons in space around the nucleus. extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. © 2006 Brooks/Cole - Thomson  8 The modern view of the atom was developed by Ernest Rutherford of New Zealand (1871-1937). © 2006 Brooks/Cole - Thomson  Ernest Rutherford 9 Canterbury University in Christchurch, NZ Rutherford laboratory © 2006 Brooks/Cole - Thomson  10 The modern view of the atom was developed by Ernest Rutherford (1871-1937). Screen 2.9 © 2006 Brooks/Cole - Thomson  11 Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Atomic number Al Atom symbol 26.981 Atomic weight © 2006 Brooks/Cole - Thomson  12 Atomic Weight This tells us the mass of one atom of an element relative to one atom of another element. OR — the mass of 1000 atoms of one relative to 1000 atoms of another. For example, an O atom is approximately 16 times heavier than an H atom. Define one element as the standard against which all others are measured Standard = carbon © 2006 Brooks/Cole - Thomson  13 Mass Number, A C atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units (u) Mass Number (A) = # protons + # neutrons A boron atom can have A = 5 p + 5 n = 10 u A 10 B Z 5 © 2006 Brooks/Cole - Thomson  Boron in Death Valley 14 Death Valley has been a major source of borax and other boron-containing minerals. Borax was transported out of Death Valley in wagons pulled by teams of 20 mules. © 2006 Brooks/Cole - Thomson  15 Isotopes Atoms of the same element (same Z) but different mass number (A). Boron-10 has 5 p and 5 n: 105B Boron-11 has 5 p and 6 n: 115B 11B 10B © 2006 Brooks/Cole - Thomson  Hydrogen Isotopes 16 Hydrogen has _____ isotopes 1 proton and 0 1 H neutrons, protium 1 1 proton and 1 2 H neutron, deuterium 1 1 proton and 2 3 H 1 neutrons, tritium radioactive © 2006 Brooks/Cole - Thomson  17 Isotope Composition Isotope Electrons Protons Neutrons Sulfur-32 Bromine- 79 © 2006 Brooks/Cole - Thomson  18 Isotopes & Their Uses Heart scans with radioactive technetium-99. 43Tc 99 Emits gamma rays © 2006 Brooks/Cole - Thomson  19 Masses of Isotopes determined with a mass spectrometer © 2006 Brooks/Cole - Thomson  20 Mass spectrum of C6H5Br © 2006 Brooks/Cole - Thomson  21 11B Isotopes 10B Because of the existence of isotopes, the mass of a collection of atoms has an average value. Average mass = ATOMIC WEIGHT Boron is 19.9% 10B and 80.1% 11B. That is, 11B is 80.1 percent abundant on earth. For boron atomic weight = 0.199 (10.0 u) + 0.801 (11.0 u) = 10.8 u © 2006 Brooks/Cole - Thomson  22 Isotopes & Atomic Weight Because of the existence of isotopes, the mass of a collection of atoms has an average value. 6Li = 7.5% abundant and 7Li = 92.5% –Atomic weight of Li = ______________ 28Si = 92.23%, 29Si = 4.67%, 30Si = 3.10% –Atomic weight of Si = ______________ © 2006 Brooks/Cole - Thomson  23 Counting Atoms Mg burns in air (O2) to produce white magnesium oxide, MgO. How can we figure out how much oxide is produced from a given mass of Mg? © 2006 Brooks/Cole - Thomson  24 Counting Atoms Chemistry is a quantitative science—we need a “counting unit.” MOLE 1 mole is the amount of substance that contains as many particles (atoms, molecules) as there are in 518 g of Pb, 2.50 mol 12.0 g of 12C. © 2006 Brooks/Cole - Thomson  25 Particles in a Mole Avogadro’s Number Amedeo Avogadro 1776-1856 6.02214199 x 1023 There is Avogadro’s number of particles in a mole of any substance. © 2006 Brooks/Cole - Thomson  Molar Mass 26 1 mol of 12C = 12.00 g of C = 6.022 x 1023 atoms of C 12.00 g of 12C is its MOLAR MASS Taking into account all of the isotopes of C, the molar mass of C is 12.011 g/mol © 2006 Brooks/Cole - Thomson  27 One-mole Amounts © 2006 Brooks/Cole - Thomson  28 PROBLEM: What amount of Mg is represented by 0.200 g? How many atoms? © 2006 Brooks/Cole - Thomson  29 Periodic Table Dmitri Mendeleev developed the modern periodic table. Argued that element properties are periodic functions of their atomic weights. We now know that element properties are periodic functions of their ATOMIC NUMBERS. © 2006 Brooks/Cole - Thomson  30 Periods in the Periodic Table © 2006 Brooks/Cole - Thomson  31 Groups/Families in the Periodic Table © 2006 Brooks/Cole - Thomson  32 Regions of the Periodic Table © 2006 Brooks/Cole - Thomson  Element Abundance 33 C O Al Si Fe http://www.webelements.com/ © 2006 Brooks/Cole - Thomson  34 Hydrogen Shuttle main engines use H2 and O2 © 2006 Brooks/Cole - Thomson  35 Group 1A: Alkali Metals Li, Na, K, Rb, Cs Reaction of potassium + H2O Cutting sodium metal © 2006 Brooks/Cole - Thomson  36 Group 2A: Alkaline Earth Metals Be, Mg, Ca, Sr, Ba, Ra Magnesium Magnesium oxide © 2006 Brooks/Cole - Thomson  37 Group 3A: B, Al, Ga, In, Tl Cu Al Al resists corrosion (here in nitric acid). Gallium is one of the few metals that can be liquid at room temp. © 2006 Brooks/Cole - Thomson  38 Gems & Minerals Sapphire: Al2O3 with Fe3+ or Ti3+ impurity gives blue whereas V3+ gives violet. Ruby: Al2O3 with Cr3+ impurity © 2006 Brooks/Cole - Thomson  39 Group 4A: C, Si, Ge, Sn, Pb Quartz, SiO2 Diamond © 2006 Brooks/Cole - Thomson  40 Group 5A: N, P, As, Sb, Bi Ammonia, NH3 White and red phosphorus © 2006 Brooks/Cole - Thomson  41 Phosphorus Phosphorus first isolated by Brandt from urine, 1669 © 2006 Brooks/Cole - Thomson  42 Group 6A: O, S, Se, Te, Po Sulfuric acid dripping from snot-tite in cave in Mexico Elemental S has a ring structure. © 2006 Brooks/Cole - Thomson  43 Group 7A: Halogens F, Cl, Br, I, At © 2006 Brooks/Cole - Thomson  44 Group 8A: Noble Gases He, Ne, Ar, Kr, Xe, Rn © 2006 Brooks/Cole - Thomson  45 Transition Elements Lanthanides and actinides Iron in air gives iron(III) oxide © 2006 Brooks/Cole - Thomson  Colors of Transition Metal 46 Compounds Cobalt Nickel Copper Zinc Iron © 2006 Brooks/Cole - Thomson