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Chemical bonding • You should already know: – how to determine valence electrons – what kind of elements make up covalent and ionic bonds – which type of bond are electrons shared and which type of bond are electrons transferred – which elements gain electrons and which lose electrons Chemical bonding • The valence shell becomes stable with 8 electrons except H and He (2 e-) • The goal to achieve a full outer shell drives the formation of bonds between atoms • Atoms with full valence shells have filled s and p orbitals Draw a Bohr diagram for Ne Write the Draw a Lewis electron Dot diagram for configuration for Ne Ne; Highlight the valence shell configuration Draw a Bohr diagram for Ne Write the Draw a Lewis electron Dot diagram for configuration for Ne Ne; Highlight the valence shell configuration 2 2 1s 2s 2p 6 Ne Lewis Structures-Covalent N O N B O N D I N G P A I R S BONDING ELECTRONS N O N B O N D I N G P A I R S Lewis Structures-covalent SHARED BONDING ELECTRONS (are attracted to both nuclei) Lewis Structures-covalent MOLECULES ARE USUALLY DRAWN THIS WAY; THE LINE REPRESENTS THE SHARED PAIR OF ELECTRONS IN A COVALENT BOND Lewis Structures-covalent SOME BOOKS OMIT THE NONBONDING ELECTRONS FOR SIMPLICITY Draw Lewis Structures for the following Covalent Compounds Phosphorus + chlorine P + Cl Phosphorus + chlorine Cl P Cl Cl Oxygen and chlorine Hydrogen and bromine Hydrogen and oxygen Hydrogen and chlorine Carbon and fluorine Hydrogen and carbon Sulfur and oxygen Silicon and fluorine Sulfur and bromine Lewis Structure-ionic compounds X Na + Cl + Na Cl X KCl x K + K + Cl Cl x - MgF2 2+ Mg x Mg x x F + F - x F AlF3 Na3N MgO Al2O3 LiBr BaCl2 BONDING REACTIONS WORKSHEET Indicate Ionic or Covalent then draw the Lewis Structure for each 1) Sodium and chlorine 2) Potassium and fluorine 3)Lithium and sulfur 4) Carbon and hydrogen 5) Beryllium and sulfur 6) Magnesium and nitrogen 7) Sulfur and fluorine 8) Aluminum and nitrogen 9) Carbon and chlorine 10) Carbon and fluorine 11) Sulfur and oxygen 12) Sulfur and hydrogen 13) Calcium and chlorine 14) Magnesium and phosphorus 15) Phosphorus and hydrogen 16) Challenge. Draw a Lewis structure with two carbons and six hydrogens Guidelines for Lewis Structures • The lesser amount of an element gets placed in the middle of the molecule (everything bonds to it) • Hydrogen NEVER gets placed in the middle Guidelines for Lewis Structures • Carbon is always placed in the middle of the molecule (multiple carbons are bonded together in a chain) Some common elements and their number of bonds • Hydrogen only produces one bond • Oxygen produces 2 bonds (group 16) • Carbon must have four bonds (group14) • Nitrogen must have 3 bonds (gr. 15) Some common elements and their number of bonds • In general, one can use similarities found in groups to determine number of bonds • You also can draw an elements electron-dot structure to determine number of bonds H2O CH4 PCl3 NH3 CH3NH2 HBr H2Se Cl2 N2H4 CH3OH CHEMICAL REACTIONS • A physical change does not change the substance • A chemical change (AKA chemical reaction) does change the substance • Chemical changes are accompanied by physical changes Processes that are physical changes • Evaporation • Condensation • Melting • Freezing • boiling CHEMICAL REACTIONS happen around you everyday… • RXNs can be used to heat a home, power a car, manufacture fabrics for clothing, make medicines, and produce paints and dyes in your favorite colors • RXNs provide NRG for walking, running, working, and thinking Signs of a Chemical Reaction None of the clues alone prove a RXN has occurred because some physical changes such as boiling involve one or more of these signs. 1) 2) 3) 4) 5) Signs of a Chemical Reaction Color changes precipitation of a solid Production of sound odor changes gas release Signs of a Chemical Reaction 6) release of heat 7) release of light 8) Absorption or release of electrical energy 9) Reduction or increase in temperature A chemical analysis that shows the formation of a new substance would be good lab evidence that new products were formed Chemical Equations • Any substance that undergoes a reaction is called a REACTANT • When reactants undergo a chemical change, each new substance formed is called a PRODUCT Chemical Equations Examples Molecules in wood + oxygen NRG + water + carbon dioxide In your body: Glucose + oxygen NRG + water + carbon dioxide Signs of a chemical reaction don’t completely describe what happens during a RXN Chemists represent the changes taking place in a reaction by writing equations WORD EQUATIONS Acetic Acid + sodium hydrogen carbonate sodium acetate + water + carbon dioxide RED= REACTANTS BLUE= PRODUCTS = YIELDS/PRODUCES CHEMICAL EQUATIONS HC2H3O2 + NaHCO3 NaC2H3O2 + H2O + CO2 Be examining a chemical equation, you can determine exactly what elements make up the substances that react and form. Physical State HC2H3O2 (aq) + NaHCO3 (s) NaC2H3O2 (aq) + H2O (l) + CO2 (g) Symbols in parentheses are put after the formulas to indicate the state of the substance. Symbol Meaning Produces or yields Reversible RXN Heat Reactants are heated, temperature not specified (s), (g), Symbols for solid, gas, liquid (l), (aq) Pd Substance dissolved in water Chemical formula of a catalyst; a substance added to speed up a RXN NRG and chemical equations • Noticeable amounts of energy are absorbed or released during a chemical reaction. • If NRG is absorbed in the RXN, it is endothermic • If NRG is released in the RXN, it is exothermic NRG and chemical equations 2H2O (l) + NRG 2H2(g) + O2(g) • When NRG is absorbed, NRG is written as a reactant NRG and chemical equations CH4 (g) + 2O2(g) CO2(g) + 2H2O(g) + NRG When energy is released, NRG is written as a product SOME FORMS OF ENERGY ARE LIGHT, HEAT, SOUND, ELECTRICAL Once you finish the notes complete the sheets in baskets #6 ( Concept Review: Describing Chemical Equations WS) Balancing Chemical Equations http://misterguch. brinkster.net/eqnb alance.html Law of Conservation of Mass Matter is During a neither created chemical nor destroyed reaction, atoms during a are rearranged, chemical not destroyed. reaction. The mass of the stuff that you make in a chemical reaction is the same as the mass of the stuff that you start with). This is called the Law of Conservation of Mass Balancing Chemical Equations Get yourself an unbalanced equation Balancing Chemical Equations Draw boxes around all the chemical formulas. Never, ever, change anything inside the boxes. Ever. Really. If you do, you're guaranteed to get the answer wrong. Balancing Chemical Equations Make an element inventory. You have to make an inventory of how many atoms of each element you have, and then you have to keep it current throughout the whole problem. Balancing Chemical Equations Write numbers in front of each of the boxes until the inventory for each element is the same both before and after the reaction. Balancing Chemical Equations Whenever you change a number, make sure to update the inventory - otherwise, you run the risk of balancing it incorrectly. Balancing Chemical Equations When all the numbers in the inventory balance, then the equation can balance, NH4Cl + NaNO2 NaCl + N2 + H2O Cl + NaOH NaCl + NaClO + H2O Cl + NaOH NaCl + NaClO + H2O Pb(NO3)2 PbO + NO2 + O2 Hg2O + O2 HgO CaO + MgCl2 MgO + CaCl2 Ca + H2O Ca(OH)2 + H2 CrCl3 + H2SO4 Cr(SO 4)3 + HCl Fe(NO3)3 + NH 4OH Fe(OH)3 + NH4NO3 AlCl3 + K3 PO4 AlPO4 + KCl Al2O3 + C + Cl2 CO + AlCl3 Cu2O + HCl + CuCl + H2O Mg(HCO3)2 + HCl MgCl2 + H2O + CO2 Fe + O2 Fe2O3 Si + H2O SiO2 + H2 Writing Word Equations From Chemical Equations take out your polyatomic ion sheet from last semester HC2H3O2(aq) + NaHCO3(s) NaC2H3O2(aq) + H2O(l) + CO2(g) Xe (g) + 3F2(g) XeF6 (s) 2H2O(l) + nrg 2H2(g) + O2(g) CH4 (g) + 2O2(g) CO2(g) + 2H2O(g) + NRG H2CO3(aq) H2O(l) + CO2(g) 2NaOH (aq) + CO2(g) Na2CO3 (s) + H2O(l) C (s) +O2 (g) CO2(g) 2H2(g) + O2(g) 2H2O(g) + NRG MgCl2(aq) + 2AgNO3 (aq) Mg(NO3)2 (aq) + 2AgCl(s) AgNO3 (aq) + NaBr (aq) AgBr(s) + NaNO3(aq) C5H12 (l) +8O2(g) 5CO2(g) + 6H2O(g) CoCO3 (s) + NRG CoO(s) + CO2(g) BaCO3(s) + C(s) + H2O(g) 2CO(g) + Ba(OH)2(s) Word Equations Notes EVERY EQUATION FOLLOWS THIS PATTERN REACTANTS PRODUCTS Word Equations Notes A+ SIGN ON THE REACTANT SIDE MEANS “REACTS WITH” A + SIGN ON THE PRODUCT SIDE MEANS “AND” Word Equations Notes H2O (l) = WATER H2O(g) = WATER VAPOR H20(s) = ICE DIATOMIC ELEMENTS… ARE ELEMENTS THAT EXIST IS NATURE AS A MOLECULE OF TWO ATOMS OF THEMSELVES BONDED TOGETHER DIATOMIC ELEMENTS MEMORIZE THESE: H2(g)= HYDROGEN GAS N2(g)= NITROGEN GAS O2 (g)= OXYGEN GAS F2(g)= FLUORINE GAS Cl2(g)= CHLORINE GAS Br2(g)= BROMINE GAS I2 (g)= IODINE GAS Writing Word Equations From Chemical Equations take out your polyatomic ion sheet from last semester HC2H3O2(aq) + NaHCO3(s) NaC2H3O2(aq) + H2O(l) + CO2(g) Xe (g) + 3F2(g) XeF6 (s) 2H2O(l) + nrg + O2(g) 2H2(g) CH4 (g) + 2O2(g) 2H2O(g) + NRG CO2(g) + H2CO3(aq) H2O(l) + CO2(g) 2NaOH (aq) + CO2(g) Na2CO3 (s) + H2O(l) C (s) +O2 (g) CO2(g) 2H2(g) + O2(g) NRG 2H2O(g) + MgCl2(aq) + 2AgNO3 (aq) Mg(NO3)2 (aq) + 2AgCl(s) AgNO3 (aq) + NaBr (aq) AgBr(s) + NaNO3(aq) C5H12 (l) +8O2(g) 5CO2(g) + 6H2O(g) CoCO3 (s) + NRG + CO2(g) CoO(s) BaCO3(s) + C(s) + H2O(g) 2CO(g) + Ba(OH)2(s) More Practice Writing Word Equations: Balance each first MgBr2 (aq) + Cl2 (g) MgCl2 (aq) + Br2(g) Fe(s) + O2(g) Fe2O3(s) H2O(l) + N2O3(g) HNO2(aq) Na2O(s) + H2O(l) NaOH(aq) Fe(s) + H2O(l) Fe3O4(s) + H2(g) Write balanced chemical equations from word equations 1) Aqueous magnesium bromide reacts with chlorine gas to produce aqueous magnesium chloride and bromine gas. 2) Chlorine gas reacts with solid sodium iodide to produce solid sodium chloride and iodine gas. 3) Solid potassium nitrate produces solid potassium nitrate and oxygen gas 4) Solid zinc reacts with aqueous hydrogen monochloride to produce aqueous zinc(I) chloride and hydrogen gas 5) Solid calcium oxide reacts with aqueous hydrogen monochloride to produce aqueous calcium chloride and water. 6) Solid sodium reacts with chlorine gas to produce solid sodium chloride. 7) Bromine gas reacts with water and sulfur dioxide gas to produce aqueous hydrogen monobromide and aqueous hydrogen sulfate. 8) Solid calcium oxide reacts with water to produce aqueous calcium hydroxide. 9) Solid diphosphorus pentaoxide reacts with solid barium oxide to produce solid barium phosphate. 10) Solid iron reacts with liquid sulfur to produce solid iron(II)sulfide 11) Solid sodium reacts with water to produce aqueous sodium hydroxide and hydrogen gas. 12) Aqueous copper(I)chloride reacts with dihydrogen sulfide gas to produce solid copper(I)sulfide and aqueous hydrogen monochloride. 13) Solid aluminum reacts with aqueous lead(II)nitrate to produce aqueous aluminum nitrate and solid lead. 14) Solid magnesium reacts with oxygen gas to produce solid magnesiumoxide. 15) Aqueous hydrogen carbonate produces carbon dioxide gas and water. Types of Reactions: --Distinguish between the 5 major type of chemical reactions --Classify a reaction as belonging to one of the 5 major types What is a reactant? Any substance that undergoes a reaction 5 MAJOR CLASSES OF RXNS SYNTHESIS DECOMPOSITION SINGLE DISPLACEMENT DOUBLE DISPLACEMENT COMBUSTION SYNTHESIS 2 OR MORE SUBSTANCES COMBINE TO FORM ONE PRODUCT. (2 or more reactant yields 1 product) EX: 3Fe(s) + O2(g) Fe3O2(s) + Decomposition 1 reactant is broken down into 2 or more products. EX: 2H2O(l) 2H2(g) + O2(g) EX: 2H2O(l) 2H2(g) + O2(g) + Single displacement a.k.a. single replacement 2 reacts, 1 is an element and the other is a compound, 2 products, one is an element the other a compound. The metal element takes the place of the metal element in the compound OR nonmetal replaces nonmetal Single displacement EX: Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s) + + DOUBLE DISPLACEMENT a.k.a. DOUBLE REPLACMENT THE POSITIVE IONS OF TWO IONIC COMPOUNDS ARE INTERCHANGED. AT LEAST ONE PRODUCT MUST BE WATER OR A PRECIPITATE Double displacement EX: PbCl2(s) + Li2SO4(aq) PbSO4(s) + 2LiCl(aq) + + Combustion Means burning in oxygen; products will be carbon dioxide CO2 and water H2O Identify each reaction type below 1. 2. 3. 4. 5. 6. 7. 8. A+B AB A + BC B + AC X + YZ Z + YX MN + OP MP + ON CH + O2 CO2 + H2O XY X+Y S+T ST G + HI H + GI 1. Synthesis 2. Single replacement 3. Single replacement 4. Decomposition 5. Decomposition 6. Decomposition 7. Double replacement 8. Synthesis 9. Double replacement 10. Double replacement 11. Single replacement 12. 13. 14. 15. single replacement single replacement double replacement single replacement BALANCE EACH EQUATION AND IDENTIFY THE TYPE ANSWER KEY