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Chapter 4: Periodic Table I. History of Development A. Mendeleev – Beginnings of the Modern Periodic Table 1. Organization 2. Elements were arranged in order of increasing atomic mass 3. Predicted the existence of undiscovered elements 4. Properties of the elements seemed to repeat each other II. Modern Periodic Table A. Organization 1. rows (7) = Periods 2. columns (18) = Groups and Families (7) 3. staircase = division between metals, nonmetals, and metalloids (semi-metals) 4. Modern Periodic Law: 5. Atomic Number vs Atomic Mass 6. Elements are arranged in order of increasing atomic number 7. Why does the table include the term “Periodic”? B. Electron Configurations and the Periodic Table 1. Patterns 2. Noble gas or “Core” configurations C. Electron Dot diagrams and the Periodic Table 1. pattern D. Oxidation States (Valence) and the Periodic Table 1. Octet Rule 2. Patterns 3. Positive vs Negative Ions 4. Elements with multiple oxidation states E. Metals vs Non-metals vs Metalloids (Semi-metals) 1. Metals a. left of the staircase b. 1-3 electrons in their outermost energy level (excluding “d” electrons) c. electron donors: lose e- d. form positive ions by losing electrons (cations) e. hard and shiny f. good conductors of heat and electricity g. most are solids, malleable and ductile h. high melting and boiling points 2. Non-metals a. right of the staircase b. 5-8 electrons in their outermost energy level c. electron acceptors: gain e- d. form negative ions (anions) e. poor conductors of heat and electricity f. generally gases or brittle solids g. low melting and boiling points 3. Metalloids (Semimetals) = have properties of both metals and non-metals III. Trends or Patterns in the Periodic Table A. Certain properties of elements in the periodic table follow a predictable pattern. Both chemical and physical properties of an element can be predicted by its “placement” in the table. B. Atomic Radius and the Periodic Table = atom size 1. patterns: increases from top to bottom and right to left 2. explanations: top to bottom (adding energy levels increases atomic radius); right to left (adding protons pulls energy levels in closer, decreasing atom size) 3. atoms and positive/negative ions: positive ions are smaller than their neutral atoms; negative ions are larger than their neutral atoms C. Ionization Energy and the Periodic Table = energy needed to remove the outermost electron 1. patterns: increases from bottom to top and left to right 2. explanations: bottom to top - in higher energy levels, e- are farther from the nucleus – held less tightly, more “shielding effect”; left to right – metals lose e- more easily than nonmetals which tend to gain e- D. Electron Affinity and the Periodic Table = attraction for e- (negative) 1. patterns (weak) – in general, increases from left to right 2. explanations: metals tend to lose e; non-metals tend to gain eE. Electronegativity and the Periodic Table = attraction for e- when bonded to another atom 1. patterns: increases from bottom to top and left to right 2. explanations – see ionization energy F. Chemical Reactivity and the Periodic Table – ability to form bonds with other atoms/elements 1. patterns metals: increases from top to bottom and right to left nonmetals: increases from bottom to top and left to right 2. explanations – ability to gain or lose eIV. Chemical Families and their Characteristics – A. Alkali Metals (Group 1, or IA) 1. most reactive metals 2. oxidation state = 1+ 3. react with water to form hydrogen gas and a base K + H2O H2 + KOH (base) (alkali) 4. shiny, silvery soft solids that are malleable, ductile, and good conductors of heat and electricity 5. sodium and potassium are the most abundant 6. sodium compounds are important commercially: NaOH – paper; NaCO3 – glass; NaSiO3 – soaps B. Alkaline Earth Metals (Group 2, IIA) 1. oxidation state = 2+ 2. reactive, but not as reactive as alkali metals 3. most abundant are magnesium and calcium which occur widely in minerals (CaCO3, MgCO3) 4. CaO is used in steel and cement and in liming lakes to reduce acid rain 5. CaCl2 is used to “salt” roads B. Halogens (Group 17, VIIA) C. Halogens (Group 17, VIIA) 1. most reactive nonmetals 2. -1 oxidation state 3. Chlorine has many industrial uses 4. diatomic = Cl2, F2, I2, etc. 5. reaction of most metals with the halogens forms “salts” 6. fluorine is the most reactive nonmetal element 7. chlorine is used to kill bacteria in drinking water 8. chlorofluorocarbons – refrigerants and aerosols (replaced because they destroy the ozone layer) D. Noble (Inert) Gases (Group 18, VIIIA) 1. least reactive group of elements – energy levels and orbitals are filled 2. Helium is the most important 3. Can be used to protect active metals in welding 4. Used in colored lights E. Transition metals (Group 3-12, IIIB-IIB) 1. largest “family” 2. building or structural metals 3. multiple oxidation states because of losing “d” electrons 4. commonly mixed in “alloys” 5. zinc and chromium are “corrosion” resistant (resist oxidation) 6. iron = 4th most abundant element in earth’s crust Fe2O3); iron + carbon + other metals = steel; Fe in hemoglobin 7. coinage metals are Cu, Ag, Au 8. adding “d” electrons F. Inner Transition Metals (Lathanides and Actinides) 1. Lanthanides – 3+ ions; soft, silvery metals; fairly reactive; fairly common in nature 2.Actinides – most are radioactive; most are synthetic produced from bombarding uranium with protons G. Chalcogens (Oxygen group) (Group 16 or VIA) 1. most plentiful element in earth’s crust (FeO, CaCO3, etc) 2. needed as a gas for aerobic respiration (O2) 3. reactive, removes two electrons from other elements to form O2- (oxidation) 4. O3 = ozone (pollutant in photochemical smog; high in the atmosphere it protects us from uv radiation) 5. O2 composes 21% of our atmosphere, produced primarily from photosynthesis by plants 6. sulfur compounds are important commercially (H2SO4) = sulfuric acid; sulfur oxides are produced from the burning of fossil fuels and contribute to the formation of acid rain SO2 + H2O H2SO3 SO3 + H2O H2SO4 H. Hydrogen is its own family 1. it can either gain or lose an electron 2. H H+ and e3. H + e- H4. it can form covalent bonds by sharing electrons H + H H2 5. Hydrogen gas is being used as an alternative fuel (very reactive) H2 + O2 H2O + energy I. Carbon group (group IVA, 14) 1. carbon = basis of all organic molecules (most molecules in living organisms are based upon carbon) 2. easily forms 4 covalent bonds 3. two main inorganic forms: diamond and graphite (allotropes) 4. forms 5 main types of organic molecules: hydrocarbons, lipids, proteins, nucleic acids, and carbohydrates 5. silicon a. metalloid or semimetal b. abundant in earth’s crust (SiO2) – quartz c. important in computer chips J. Nitrogen group (VA, 15) 1. nitrogen is important in proteins and nucleic acids (organic molecules) 2. nitrogen compounds are important plant fertilizers and are used in explosives (TNT, dynamite)