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Molecular Compounds

Molecular Compounds. Molecular Compounds. Composed of all nonmetals Single unit = Molecule Held together by covalent bonds Atoms share pairs of electrons They can share 1, 2, or 3 pairs of electrons to form single, double or triple covalent bonds.

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Molecular Compounds

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  1. Molecular Compounds

  2. Molecular Compounds • Composed of all nonmetals • Single unit = Molecule • Held together by covalent bonds • Atoms share pairs of electrons • They can share 1, 2, or 3 pairs of electrons to form single, double or triple covalent bonds. • Two of the same elements can combine in different ratios to form different molecular compounds. • Ex. • Carbon dioxide = CO2 • Carbon monoxide = CO

  3. Examples of Molecular Compounds • Common Names • H2O, water • NH3, ammonia • CH4, methane • C2H6, ethane • C3H8, propane • C6H12O6, glucose • C8H10N4O2, caffeine • C6H8O6, ascorbic acid (vitamin C)

  4. Organic Compounds and Hydrocarbons • Organic Compound: • A molecule primarily made from carbon and hydrogen, but often with some oxygen, nitrogen, or some other nonmetal element. • Ex. Ethanol = C2H5OH • Hydrocarbon: • An organic compound that contains only hydrogen and carbon atoms. • Ex. Paraffin Wax = C20H42

  5. Naming & Writing Formulas for Binary Molecular Compounds • Prefixes = Subscripts • Add prefixes to beginning of element’s name to indicate # of atoms in a molecule • Use –ide ending on second element

  6. Naming & Writing Formulas for Binary Molecular Compounds • If the subscript for the first element is greater than one, indicate the subscript with a prefix. We do not write mono- on the first name. • Leave the "a" off the end of the prefixes that end in "a" and the “o” off of mono- if they are placed in front of an element that begins with a vowel (oxygen or iodine).

  7. Prefixes • 1 = mono • 2 = di • 3 = tri • 4 = tetra • 5 = penta • 6 = hexa • 7 = hepta • 8 = octa • 9 = nona • 10 = deca

  8. Examples: • Answers: • Nitrogen dioxide • Dinitrogen monoxide • Diphosphorustrichloride • Sulfur hexafluoride • Name the following:NO2 N2O P2Cl3 SF6

  9. Learning Check: • CO2 • S2F4 • C6H8 • Diphosphorusoctoxide • Sulfur trioxide • Tetracarbonheptahydride Write the formulas: • Carbon dioxide • Disulfurtetrafluoride • Hexacarbonoctahydride Name the following compounds: • P2O8 • SO3 • C4H7

  10. Covalent Bonds • A link between atoms due to the sharing of two electrons. This bond forms between atoms of two nonmetals. • There are two types of covalent bonds: • Polar Covalent Bonds • Nonpolar Covalent Bonds • The type of bond formed is dependent on the difference between the electronegativities of the elements forming the compounds.

  11. Differences in Electronegativity

  12. Ionic, Polar or Nonpolar? HF H2O NH3 Cl2 CO2

  13. Non-polar Covalent Bonds • The electrons are shared equally, there is a even distribution of the negative charge for the electrons in the bond, so there is no partial charges on the atoms.

  14. Polar Covalent Bonds • One atom in the bond attracts electrons more than the other atom, the electron negative charge shifts to that atom giving it a partial negative charge. The other atom loses negative charge giving it a partial positive charge.

  15. Polar Covalent Bonding • d+ means a partially positive • d- means a partially negative d+ d- H Cl • The Cl pulls harder on the electrons • The electrons spend more time near the Cl

  16. Hydrogen Bonding in Water • The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond. • Each water molecule can form hydrogen bonds with up to four neighbors.

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