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Atoms and the Periodic Table: Element Classification and Chemical Compounds

This chapter discusses the classification of elements as metals, nonmetals, and metalloids, their properties, and the formation of chemical compounds. It also covers isotopes and how to calculate the average atomic mass.

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Atoms and the Periodic Table: Element Classification and Chemical Compounds

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  1. Chapter 2 Atoms and the Periodic Table CHE 101 Sleevi

  2. Atoms and the Periodic Table • Element • Substance that cannot be broken down into simpler substances by a chemical reaction • Identified by a one or two letter symbol • 1st letter capitalized • 2nd letter, if present, lowercase • Position on the periodic table based on chemical properties

  3. Atoms and the Periodic Table 3

  4. The Periodic Table http://www.theodoregray.com/PeriodicTable/index.html http://www.rsc.org/chemsoc/visualelements/pages/pertable_fla.htm

  5. Elements and the Periodic Table • Metals • Left of the stair-step line on the periodic table • Shiny (lustrous) • Malleable • Solids at room temperature except Hg which is a liquid • Good conductors of heat and electricity

  6. Elements and the Periodic Table • Nonmetals • Right of the stair-step line on the periodic table • Usually not shiny • Can be solids, liquids or gases at room temperature (Br is the only liquid nonmetal) • Poor conductors of heat and electricity

  7. Elements and the Periodic Table • Metalloids • Elements that abut the stair-step line on the periodic table • Have properties that are intermediate between metals and nonmetals • Silicon is brittle, but conducts electricity, is a shiny blackish silver color

  8. Elements and the Periodic Table Lecture Problem #1: Classify the following elements as metal, nonmetal or metalloid. • Lithium • Chlorine • Molybdenum • Hydrogen • Arsenic

  9. Elements of Biological Interest • Building block elements • Comprise 96% of mass of human body • C, O, H, N • Major nutrients (> 100 mg/day) • K, Na, Cl, Mg, S, Ca, P • Trace elements (< 15 mg/day) • As, B, Cr, Co, Cu F, I, Fe, Mn, Mo, Ni, Se, Si, Zn

  10. Other Elements of Interest • Most abundant elements on Earth • O, Si, Al, Fe, Ca, Na, K, Mg, H, Ti • Make up 98.9% of mass of the crust, ocean and atmosphere

  11. Elements and the Periodic Table • Compounds • Substance formed by chemically combining two or more elements together • Use chemical symbols to describe the compound • Symbols identify the types of elements (atoms) in the compound • Subscripts show the ratio of the number of each type of atom in the smallest representative particle of the element

  12. Chemical Formulas • Examples H2O one molecule contains two H atoms one O atom C3H6 one molecule contains three C atoms six H atoms

  13. Chemical Formulas Lecture Problem #2 State the number of atoms of C and H in the following: • One molecule of C4H10 • Ten molecules of C4H10

  14. Representations of Chemical Compounds Typical colors used for atoms:

  15. Atomic Structure • Since the late 19th Century, experimental evidence has determined the atom is composed of particles

  16. Characteristics of Fundamental Subatomic Particles 16

  17. Structure of the Atom Nucleus: Electron cloud: • location of protons andneutrons • dense core of the atom • location of most of the atom’s mass • location of electrons • comprises most of the atom’s volume 17

  18. Atomic Structure • Atoms are neutral (#p = #e-) • Nucleus is central, dense core of the atom • Most of the mass of the atom is in the nucleus • Mass of electrons negligible compared to mass of nucleus • Chemical properties dependent upon the electrons

  19. Identification of Atoms • Atomic number (Z) • Number of protons • Identifies the element • Mass number (A) = # of protons + # of neutrons • In neutral atom: # of protons = # of electrons

  20. Structure of the AtomAtomic Number From the periodic table: Atomic number (Z) is the number of protons in the nucleus. 3 Li • Every atom of a given element has the same atomic number. • Every atom of a given element has the same number of protons in the nucleus. • Different elements have different atomic numbers. 20

  21. Quick Review Lecture Problem #3

  22. Isotopes • Atoms with same atomic number but different mass number (different number of neutrons • Chemically alike 6C 12 Z = atomic number A = mass number Z = # p = 6 A = # p + # n = 12 22

  23. Isotopes Isotopes often listed as: element name – mass number carbon-14 nitrogen-14 uranium-238 C-12 Pb-207 Write the chemical symbols for these isotopes, including both atomic number and mass number 23

  24. Data on the Periodic Table Note: • atomic weight also called atomic mass or average atomic mass • Mass number does NOT appear on the periodic table atomic number (Z) 6 C 12.01 element symbol atomic weight (amu)

  25. Data on the Periodic Table Lecture Problems #4-5

  26. Data on the Periodic Table #5. For the isotopes in #4 write the isotope symbol (include both mass number and atomic number)

  27. Average Atomic Massaka Atomic Weight • Weighted average of the mass of the stable, naturally occurring isotopes of an element Ave at mass = Σ (rel. abund. * isotope mass) • Mass units for individual atoms in atomic mass units (1 amu) 1 amu = 1/12 the mass of a C-12 atom

  28. Calculating the Average Atomic Mass • Data needed • Number of isotopes • Relative abundance of each isotope • Isotope mass • Calculation • Weighted average • Sum of products of rel abundance and isotope mass

  29. Calculating the Average Atomic Mass Lecture Problem #6

  30. The Modern Periodic Table • Based on work of Mendeleev, 1869 • about 65 known elements • arranged elements based on trends in physical and chemical properties • left spaces for other elements, not yet discovered • generally organized according to increasing atomic weight 30

  31. 31

  32. Modern Periodic Table • Numerous people worked on periodic table at this time • Henry Moseley, British Physicist, 1913 • determined nuclear charge of atoms (Z) • arranged elements in order of increasing atomic number 32

  33. Periodic Law • When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties 33

  34. Tour of the Periodic Table

  35. Structure of the Periodic Table • Group • Vertical columns • Number appears above the column • Period • Row • May or not have written number • 1st period contains H and He

  36. Group Names • Main group elements • Also called representative elements • Designated by Group numbers 1A – 8A • Transition Metal elements • Short columns in the middle (“short stack”) • Designated by Group numbers ending in B • Inner transition elements • Lanthanide and actinide series • No group numbers

  37. Noble Gases Alkaline Earth Metals 3A 4A 5A 6A 8A 7A 1A 2A Halogens Transition Metals Alkali Metals Inner Transition Metals Metalloids Periodic Table of the Elements 3B 4B 5B 6B 8B 1B 2B 7B 37

  38. Group Names of the Main Group Elements

  39. Group Names of the Main Group Elements

  40. Location of the Elements • Since periodic table is a grid, elements can be located by “coordinates” of their group number and period number • name the element in Group 2A, period 3 • name the element in Group 5B, period 4 • Element properties can be identified by knowing its group • name the group for Mg • name the group for Ne 40

  41. Location of the Elements Lecture Problems #7, 8 7. Name the group where you find: • Mg • Ne • Br • K • Pt

  42. Location of the Elements 8. Name the elemente located in: a. Group 2A, Period 3 b. Group 5B, Period 4

  43. Allotropes of Phosphorus By Weißer_Phosphor.JPG: BXXXD at de.wikipedia Phosphor_rot.jpg: Tomihahndorf Phosphor-rot-violett.jpg: Maksim derivative work: Materialscientist [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3APhosphComby.jpg White phosphorus can be transformed to red, black or violet by in creasing temperature or pressure

  44. Modern Atomic Theory and Electron Configurations • 1911 – Rutherford’s Gold Foil Expt • 1913 – Bohr proposed fixed orbits for electrons based on energy • studied hydrogen emission spectrum • Bohr’s model did not resolve all observations • Early 1900’s – Birth of Quantum Mechanics • 1926 – Schrödinger proposed quantum mechanical model of the atom 45

  45. Quantum Mechanical Model of the Atom • Principal energy levels (shells) • correspond to the discrete energy levels in the atom that can be occupied by electrons • designated by quantum number n (n = 1, 2, 3, 4, …) • contain sublevels • quantum number n designates number of sublevels at that energy level • Sublevels (subshells) • correspond to orbital type within a principal energy level (s, p, d, f) 46

  46. Orbitals • Solution to the Schrödinger equation • Shape describes the probability of where electron will be found in space, at that energy • Overlay the nucleus • Increase in size as the principle energy level increases • Contain no more than 2 electrons 47

  47. Electronic StructureOrbital Shapes • Thes orbital has a spherical shape. • Thep orbital has a dumbbell shape. 48

  48. Sublevels:Orbital Types & Shapes • s • spherical • 1 possible s orbital at a given PEL • p • dumbbell • 3 possible p orbitals at a given PEL px, py, pz • d • more complex, multiple lobes • 5 possible d orbitals at a given PEL 49

  49. Energy Levels in an Atom 50

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