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Bonding and Chemical Reactions

Bonding and Chemical Reactions. Chapters 6 and 7. Compounds and Molecules. Chemical structure : the arrangement of atoms in a substance Chemical Bond : forces that hold atoms together in a compound. Bond Models. bond length : models distance between nucleus of 2 atoms

noelle-williamson
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Bonding and Chemical Reactions

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  1. Bonding and Chemical Reactions Chapters 6 and 7

  2. Compounds and Molecules • Chemical structure: the arrangement of atoms in a substance • Chemical Bond: forces that hold atoms together in a compound

  3. Bond Models • bond length: models distance between nucleus of 2 atoms • bond angle: models angle the bonds between 3 or more atoms form • space-filling: shows space that atoms take up bond angle space-filling

  4. Nature of Bonds Some bonds are stronger than others, but all bonds can: • bend • stretch • rotate without breaking

  5. Chemical Structure and Properties • compounds with networks are strong solids ex: diamond, quartz, many rocks • networked compounds have melting and boiling points ex: salts, rocks, diamonds

  6. Chemical Structure and Properties (cont’d) • Some compounds are made of bonded ions ex. NaCl (strong attraction between ions) • Some compounds are made of molecules ex: H2, O2, N2, CO2(gases with weak attraction for each other) • Hydrogen bonds are very strong

  7. Bonding • Atoms bond to gain 8 valence electrons- stable electronic configuration • 2 basic types of bonding: -ionic -covalent

  8. Ionic Bonding Ionic Bonds: between oppositely charged atoms; usually on opposite sides of the periodic table (metal and nonmetal) • transfer electrons • form networks, not molecules • conduct electricity when dissolved Lithium Flourine

  9. Covalent Bonds Covalent Bonds: share electrons; usually between 2 elements close on the periodic table (nonmetals) • nonpolar covalent bond: e- shared equally • polar covalent bond: e- shared unequally

  10. Metallic Bonding • “sea of electrons”: electrons can “float” freely between atoms; allows metals to conduct electricity well

  11. Polyatomic Ions Compounds with both ionic and covalent bonds • acts as a single unit (like ions) • parentheses group polyatomic ion in a compound • most names end in “ite” or “ate” (depending on # of oxygen atoms)

  12. Compound Names and Formulas (Compounds have specific names so you can tell how many and what atoms are in the compound/moleule)

  13. Sodium Chloride Cationis ALWAYS FIRST Anion is ALWAYS LAST Ionic Naming • Cations: the name of the element • Anions: have “ide” at the end of the element’s name • Ionic compounds must have a total charge of zero Na+1 + Cl-1 = NaCl (0 charge)

  14. Transition Metal Naming • Transition metals show their charges as Roman numerals because they can changecharge FeO = Fe+2 + O-2 Iron(II) Oxide Fe2O3= Fe+3 + O-2 Iron (III) Oxide

  15. What is the formula for Lithium oxide?Li- ____O- ____formula: _______________________

  16. What is the name for CuCl2?cation- ___________anion- ___________, ending- __________name- _____________________________

  17. Covalent Naming • To name covalent compounds, put a numerical prefix in front of the element’s name: 1- mono 6- hexa 2- di 7- hepta 3- tri 8- octa 4- tetra 9- nona 5- penta 10-deca • If only 1 cation is present, no prefix is needed • Atom to the right of the first cation ends in “ide”

  18. What is the name of H2O?_______________________

  19. Formulas • Empirical Formula: smallest whole-number ratioof atoms in a compound • Molecular Formula: how many atoms are in a molecule of a compound GLUCOSE Molecular Formula Empirical Formula C6H12O6 CH2O

  20. Organic and Biochemical Compounds • Organic compound: covalently bonded compound that contains carbon • Polymer: large molecule formed by more than 5 monomers (small units) ex. DNA

  21. Chemical Reactions • Result in rearranged atoms • Involve changes in energy • Exothermic: release energy (heat, fire, fizz, etc) • Endothermic: absorb energy (drop in temp.) -remember, chemical energy is stored in chemical bonds

  22. Endothermic Reaction Exothermic Reaction

  23. Describing Coefficients: individual atom = “atom” 2Mg  2 atoms of magnesium covalent substance = “molecule” 3CO2 3 molecules of carbon dioxide ionic substance = “unit” 4MgO  4 units of magnesium oxide Chemical Equations

  24. Chemical Equations (cont’d)

  25. Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # atoms 4. Reduce coefficients to lowest possible ratio, if necessary. 5. Double check atom balance!!!

  26. Balancing Example Al + CuCl2 Cu + AlCl3 Al Cu Cl Aluminum and copper(II) chloride form copper and aluminum chloride. 2 3 3 2 3 2 2 3 2 2   2 3  6  6  3 1 1 1 1 2 3

  27. ___ CH4 + ___ O2 ___ CO2+ ___ H2O Chemical Equations methane and oxygen yield carbon dioxide and water Products Reactants

  28. ___ Mg + ___ O2 ___MgO Balance the Reaction.

  29. ___ H2O2 ___H2O + ___ O2 Balance the reaction.

  30. Reaction Types • Synthesis: combines substances A + B AB • Decomposition: substances are broken apart AB A • Combustion: ALWAYS has O₂ as a reactant AB + O₂ AO + BO

  31. Reaction Types • Single-Replacement (single-displacement): one element takes the place of another AX + B A + BX • Double-Replacement (double-displacement): two compounds appear to exchange ions AX + BY AY + BX

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