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Chemical Bonds

Chemical Bonds. I. Why Atoms Combine Chemical Formulas Chemical Bonds Stability. 1 oxygen atom. 2 hydrogen atoms. A. Chemical Formula. Shows: 1) elements in the compound 2) ratio of their atoms. H 2 O. B. Chemical Bond.

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Chemical Bonds

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  1. Chemical Bonds I. Why Atoms Combine Chemical Formulas Chemical Bonds Stability

  2. 1 oxygen atom 2 hydrogen atoms A. Chemical Formula • Shows: 1) elements in the compound 2) ratio of their atoms H2O

  3. B. Chemical Bond • Strong attractive force between atoms or ions in a molecule or compound. • Formed by: • transferring e- (losing or gaining) • sharing e-

  4. Ne C. Stability • Octet Rule • most atoms form bonds in order to have 8 valence e- • want a full outer energy level • like the Noble Gases • Stability is the driving force behind bond formation!

  5. C. Stability • Transferring e- • Sharing e-

  6. Chemical Bonds II. Kinds of Chemical Bonds Ionic Bond Covalent Bond Comparison Chart

  7. A. Ionic Bond • Attraction between 2 oppositely charged ions. • Ions are charged atoms. • A cation is a positively charged ion (Forms when an atom loses an e-) Formed by metals. • An anion is a negatively charged ion (Forms when an atom gains an e-) Formed by nonmetals. • Ions are formed by transferring e- from a metal to a nonmetal.

  8. NaCl A. Ionic Bond • ions form a 3-D crystal lattice

  9. B. Covalent Bond • Attraction between neutral atoms. • formed by sharing e- between two nonmetals

  10. Cl2 H2O NH3 B. Covalent Bond • covalent bonds result in molecules

  11. B. Covalent Bond • Nonpolar Covalent Bond • e- are shared equally • usually identical atoms

  12. - + B. Covalent Bond • Polar Covalent Bond • e- are shared unequally between 2 different atoms • results in partial opposite charges

  13. C. Comparison Chart IONIC COVALENT shared between nonmetals transferred from metal to nonmetal Electrons high low Melting Point Soluble in Water usually not yes yes (solution or liquid) Conduct Electricity no molecules, odorous liquids & gases crystal lattice of ions, crystalline solids Other Properties Metal and Nonmetal Nonmetal ONLY Types of Elements

  14. Both types of bonds • Some compounds have a mixture of ionic and covalent bonds. • These generally contain POLYATOMIC IONS. • Polyatomic ions are groups of non-metal elements bonded covalently together that have an overall charge. • Generally polyatomic ions will form an ionic bond with metal. • They are easy to recognize because they have three or more elements in the compound. • Examples: Na3PO4, Al2(SO3)3

  15. Practice What type of compound is shown or described below? NaCl CO2 H2O Fe2O3 Ga(C2H3O2)3 High melting point Liquid or Gas Doesn’t dissolve in water Ionic Covalent Covalent Ionic Polyatomic (Both) Ionic Covalent Covalent

  16. Chemical Bonds III. Naming Molecular Compounds Molecular Names Molecular Formulas

  17. A. Molecular (Covalent) Names • Write the names of both elements. • Change the final ending to -ide. • Add prefixes to indicate subscripts. • Only use mono- prefix with second element.

  18. PREFIX mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- SUBSCRIPT 1 2 3 4 5 6 7 8 9 10 Covalent Naming Prefixes

  19. A. Molecular Names • CCl4 • N2O • SF6 • carbon tetrachloride • dinitrogen monoxide • sulfur hexafluoride

  20. B. Molecular Formulas • Write the more metallic element first. • Add subscripts according to prefixes.

  21. B. Molecular Formulas • phosphorus trichloride • dinitrogen pentoxide • dihydrogen monoxide • PCl3 • N2O5 • H2O

  22. B. Molecular Formulas • The Seven Diatomic Elements • Br2 I2 N2 Cl2 H2 O2 F2 In nature, these elements are never alone!

  23. Chemical Bonds IV. Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas

  24. A. Oxidation Number • The charge on an ion. • Indicates the # of e- gained/lost to become stable. 1+ 0 2+ 3+ 4+ 3- 2- 1-

  25. Oxidation Chart -2 -1 -3 0 +3 +1 +2 +/-4

  26. B. Ionic Names • Write the names of both elements, cation first. • Change the anion’s ending to -ide. • If there is a polyatomic ion, write the name of the polyatomic ion.

  27. B. Ionic Names • NaBr • Na2CO3 • SnCl4 • sodium bromide • sodium carbonate • tin chloride

  28. C. Ionic Formulas • Write each ion. Put the cation first. • Overall charge must equal zero. • If charges cancel, just write the symbols. • If not, crisscross the charges to find subscripts. • Use parentheses when more than one polyatomic ion is needed. • Roman numerals indicate the oxidation #.

  29. Writing Ionic Formulas • Crisscross method. • If the charges don’t balance, the number of the charge becomes the subscript for the opposite element or polyatomic ions. • Example • The charges BALANCE thus disappear. Mg +2 N-3 = Mg3N2

  30. Writing Formulas • Example 2: Al+3 SO4-2 • Remember to use parentheses when more than one polyatomic ion is needed. • Al2(SO4)3 • Example 3: Na+1 C2H3O2-1 • NaC2H3O2 • Remember If charges cancel, just write the symbols.

  31. C. Ionic Formulas • potassium chloride • magnesium nitrate • aluminum oxide • K+ Cl- KCl • Mg2+ NO3-  Mg(NO3)2 • Al3+ O-2 Al2O3

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