Chapter 18: The Representative Elements Big Idea: The structure of atoms determines their o Hydrogen properties; o Group 1A consequently, the o Group 2A behavior of elements is o Group 3A related to their o Group 4A location in the o Group 5A periodic table. In general nonmetallic o Group 6A character becomes o Group 7A more pronounced o Group 8A toward the right of the periodic table. 1 The Representative Elements 2 Chapter 18: The Representative Elements The Representative Elements 3 Chapter 18: The Representative Elements Hydrogen Electron configuration is 1s1(similar to the electron configurations of group 1A elements) Classified as a non metal Therefore it doesn’t fit into any group 4 Chapter 18: The Representative Elements Hydrogen Most H is made up of only two particles (an electron and a proton) H is the most abundant element in the universe and accounts for 89% of all atoms Little free H on earth H2 gas is so light that it moves very fast and can escape the Earth’s gravitational pull Need heavier planets to confine H2 5 Chapter 18: The Representative Elements Group 1A The Alkali Metals Electron configuration is ns1(n = period number). Lose their valence e- easily (great reducing agents). Most violently reactive of all the metals. React strongly with H2O(l); the vigor of the reaction increases down the group. The alkali metals are all too easily oxidized to be found in their free state in nature. 6 Chapter 18: The Representative Elements Group 1A Lithium Sodium Strong polarizing power Mined as rock salt Forms bonds with which is a deposit of highly covalent sodium chloride left as character ancient oceans evaporated Used in ceramics, Lubricants, Medicine Extracted using (lithium carbonate electrolysis of molten (treatment for bipolar NaCl (Downs process) disorder)) 7 Chapter 18: The Representative Elements Group 1A Important Group NaCl NaOH NaHCO3 (Baking Soda) - - HCO3 (aq) + HA(aq) A (g) + H2O(l) +CO2(g) The weak acid (HA) must be present in the dough; Some weak acids are sour milk, buttermilk, lemon jucie, or vinegar. Note: Baking powder contains a solid weak acid as well as the hydrogen carbonate therefore CO2(g) is released when water is added KNO3 ∆ 2KNO3(s) 2KNO2(s) + O2(g) 8 Chapter 18: The Representative Elements Group 1A Common Reactions Reaction with Halogens Reaction with H 2M + X2 2MX 2M + H2 2MH X2 is any halogen Reaction with N Reactions with Oxygen 6Li + N2 2Li3N 4Li + O2 2Li2O Li only Need excess Oxygen 2Na + O2 Na2O2 Reaction with Water M + O MO 2 2 2M + 2H2O 2MOH + H2 M = K, Rb, or Cs Reaction with Ions + 2M + 2H 2M+ + H2 9 Chapter 18: The Representative Elements Group 2A The Alkaline Earth Metals Electron configuration is ns2(n is the period number). All group 2 element are too reactive to occur in the uncombined state in nature. Usually found as doubly charged cations. All group 2 elements except for beryllium react with water and the vigor of the reaction increases going down the group. 10 Chapter 18: The Representative Elements Group 2A Beryllium Magnesium Calcium Has some non Found in sea Found in sea metal tendencies water water The gemstone Mg is present in The element of emerald contains the chlorophyll rigidity and Be but its green molecule construction color is caused Forms protective (bones, shells, by Cr3+ ions oxide concrete, mortar, limestone Obtained by the Obtained by electrolytic either chemical or (buildings)…) reduction of electrolytic molten beryllium reduction of its chloride compounds 11 Chapter 18: The Representative Elements Group 2A Important Compounds Mg(OH)2 (milk of magnesia) MgSO4 (epsom salt) Chlorophyll CaCO3 (calcium carbonate) Δ CaCO3(s) CaO(s) + CO2(g) CaO (quick lime) 2+ - CaO(s) +H2O(l) Ca (aq) + 2OH (aq) Ca(OH)2 (slack lime) Concrete 12 Chapter 18: The Representative Elements Group 2A Common Reactions Reaction with Reaction with N Halogens 3M + N2 M3N2 High temperatures M + X2 MX2 X2 is any halogen Reaction with Water Reaction with Oxygen M +2H2O M(OH)2 + H2 2M + O2 2MO Reaction with Ions + 2+ Reaction with H M + 2H M + H2 M + H2 MH2 13 Chapter 18: The Representative Elements Group 3A Electron configuration is ns2np1 (n is the period number). Boron and aluminum almost always have an oxidation number of +3. The heavier elements of the group are more likely to keep their s electrons and can have oxidation numbers of +1 or +3. 14 Chapter 18: The Representative Elements Group 3A Boron Aluminum High ionization energy Most abundant metallic Metalloid element in the Earth’s crust Forms covalent bonds Low density Tends to form compounds Excellent electrical that have incomplete conductor octets or are electron Commercial source of deficient aluminum is bauxite Mined as borax and kernite (Al2O3·xH2O where x ranges from 1 to 3) (Na2B4O7·xH2O x = 10 or 4) 15 Chapter 18: The Representative Elements Group 3A Important Compounds B(OH)3 (Boric Acid) Na2B4O7·10H2O(borax) Al2O3 (Aluminum oxide or alumina) 16 Chapter 18: The Representative Elements Group 3A Common Reactions Reaction with Reactions with N Halogens 2M +N2 2MN 2M +3X2 2MX3 X any halogen, TI 2 Reactions with ions gives as TIX well, + 3+ 2M + 6H 2M + 3H2 but no TII3 - 2M + 2OH + 6H2O - 2M(OH)4 + 3H2 Reactions with O 4M + 3O2 2M2O3 Chapter 18: The Representative Elements Group 4A Electron configuration is ns2np2 (n is the period number). The half filled orbital allows this group to straddle between metal and non metal. The heavier elements of the group are more likely to keep their s electrons and can have oxidation numbers of +2 or +4. 18 Chapter 18: The Representative Elements Group 4A Carbon Silicon Central element to life Central element to Nonmetallic properties electronic technology and artificial intelligences. Forms Covalent bonds with nonmetals and ionic Larger atomic size than C bonds with metals which results in relatively few compounds that Small radius allows for the wide occurrence of C=C have Si=Si and Si=O and C=O bonds in bonds. compounds 19 Chapter 18: The Representative Elements Group 4A Germanium Tin Lead Germanium is Tin is easily Lead is durable recovered from obtained from it and malleable the flue dust of ore (cassiterite which makes it industrial plants (SnO2)) by useful in the processing zinc reduction with construction ores. carbon. industry Germanium is Tin is expensive It is very dense mainly used in and not very which makes it the strong but it is ideal as semiconductor resistant to radiation shields industry. corrosion. from x rays 20 Chapter 18: The Representative Elements Group 4A Important Compounds CO2 CO Red = Silicon SiO2 (Silica) Purple = Oxygen ZnSiO4 (Zircon) CaMg5(Si4O11)2(OH)2 Silicones 21 Chapter 18: The Representative Elements Group 4A Common Reactions Reaction with Reactions with O Halogens M + O2 MO2 M +2X2 MX4 X2 = any halogen Reactions with ions molecule, + 2+ M + 2H M + H2 M = Ge or Sn; Pb M = Sn or Pb gives PbX2 22 Chapter 18: The Representative Elements Group 5A Electron configurations ns2np3 (n is the period number) Oxidation states that range from -3 to +5 The metallic character of the group increases down the group 23 Chapter 18: The Representative Elements Group 5A Nitrogen Phosphorus Rare in the Earth’s crust White phosphorus is a soft, but elemental nitrogen white, poisonous, highly (N2) is the principal reactive molecular solid component of our consisting of tetrahedral P4 atmosphere (76% by molecules. White phosphorus mass) burst into flames when N ≡ N triple bond strength exposed to air. 푘퐽 is 944 푚표푙 making it almost Red phosphorus is used in the as inert as the noble striking surfaces of matches gases. because the phosphorus ignites with friction. 24 Chapter 18: The Representative Elements Group 5A Important Compounds NH3 (ammonia) NH4NO3 (ammonium nitrate) NH2NH2 (hydrazine) NaN3 (sodium azide) PH3 N2O (nitrous oxide or laughing gas) NO (nitrogen oxide, nitrogen monoxide, or nitric oxide) NO2 HNO3 (nitric acid) H3PO4 (phosphoric acid) 25 Chapter 18: The Representative Elements Group 6A Electron configurations ns2np4 (n is the period number) Elements become increasingly more nonmetallic toward the right-hand side of the periodic table 26 Chapter 18: The Representative Elements Group 6A Rhombic Monoclinic Oxygen Sulfur Oxygen is the most abundant Sulfur behaves differently element in the Earth’s crust. than oxygen due to its increased size and The free element accounts for decreased electronegativity. 23% of the mass of the atmosphere. Sulfur also has weaker tendencies to form multiple The combustion of all living bonds to one atom. organisms in oxygen is thermodynamically Sulfur can extend its octet. spontaneous. Sulfur has a striking ability to Two allotopes of oxygen are catenate, or forms chains of atoms. O2 and O3. 27 Chapter 18: The Representative Elements Group 6A Important Compounds H2O H2O2 (hydrogen peroxide) SO2 H2SO4 SF6 (sulfur hexaflouride) S2Cl2 28 Chapter 18: The Representative Elements Group 7A The Halogens Electron configurations ns2np5 (n is the period number). In its elemental state, all halogens atoms combine to form diatomic molecules (ex. F2,I2,…). With the exception of F, the halogens can also lose valence electrons and their oxidation states can range from -1 to +7. 29 Chapter 18: The Representative Elements Group 7A Fluorine Chlorine Fluorine is the halogen with Chlorine is more soluble in greatest abundance in water than fluorine. the Earth’s crust As a result even though It occurs widely in many there is more F present minerals in the Earth’s crust the Fluorine is the most strongly oceans are salty with oxidizing element. chlorides rather than fluorides.