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Covalent Compounds

Covalent Compounds. Covalent Compounds. Usually soft and squishy Not soluble in water Does not conduct electricity Low melting points Low boiling points. Two Types of Bonds. Ionic : Electrons are lost or gained Covalent : Electrons are shared Non-polar covalent: equally shared

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Covalent Compounds

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  1. Covalent Compounds

  2. Covalent Compounds • Usually soft and squishy • Not soluble in water • Does not conduct electricity • Low melting points • Low boiling points

  3. Two Types of Bonds • Ionic: Electrons are lost or gained • Covalent: Electrons are shared • Non-polar covalent: equally shared • Polar Covalent: unevenly shared

  4. Naming Covalent Compounds

  5. NAMING COMPOUNDS Nonmetal – Nonmetal USE PREFIXES! • Change the ending of the second word to -ide • No mono on the first word • Drop any double vowels

  6. Covalent Prefixes

  7. THE PREFIX TELLS YOU HOW MANY ATOMS YOU HAVE!NO CRISS CROSS!!!!

  8. Examples Carbon Monoxide Carbon Dioxide Sulfur Dioxide Sulfur Trioxide DinitrogenTetrahydride DinitrogenTrioxide • CO • CO2 • SO2 • SO3 • N2H4 • N2O3

  9. Lewis Structures

  10. Lewis Structures for Compounds • The pair of dots between two symbols represents the shared pair. • How many shared pairs does each fluorine have below? • An unshared pair, also called a lone pair, is a pair of electrons that is not involved in bonding and that belongs exclusively to one atom.

  11. Lewis Structures • The shared pair of electrons is often replaced by a long dash. Each dash represents TWO electrons

  12. + 7e- 7e- 8e- 8e- F F F F F F F F lonepairs lonepairs single covalent bond single covalent bond lonepairs lonepairs Why should two atoms share electrons? To get a valence of 8 electrons! Lewis structure of F2

  13. Multiple Covalent Bonds • double bond:covalent bond in which two pairs of electrons are shared between two atoms • shown by two side-by-side pairs of dots or by two parallel dashes

  14. Multiple Covalent Bonds • triple bond:covalent bond in which three pairs of electrons are shared between two atoms • shown by three side-by-side pairs of dots or by three parallel dashes

  15. Steps for Drawing Lewis Structures • Draw the Lewis Dot diagram for each individual atom • Count up the number of valence electrons • Connect the atoms together to pair up the electrons (put atoms that can make the most connections in the center) • Once all electrons are paired, recount electrons to double check total valence

  16. Practice Draw the Lewis Structure for HBr 1. H Br 2. 1 + 7 = 8 3. H — Br 4. 2 + 6 = 8

  17. Bond Polarity

  18. Review:What is electronegativity? ability of an atom to attract electrons Which element is the most electronegative? Fluorine - Has 7 valence e- and wants 8 H F

  19. F H F H Polar bond : covalent bond with greater electron density around one of the two atoms electron poor region electron rich region e- rich e- poor d+ d-

  20. 1 18 2 13 14 15 16 17 3 4 5 6 7 8 9 10 11 12

  21. Increasing difference in electronegativity Covalent Ionic Polar Covalent share e- transfer e- partial transfer of e- What type of Bond is it?

  22. Classify the following bonds as ionic, polar covalent,or covalent: Cs to Cl Cs – 0.7 Cl – 3.0 3.0 – 0.7 = 2.3 Ionic H to S H – 2.1 S – 2.5 2.5 – 2.1 = 0.4 Polar Covalent Cl to N Cl– 3.0 N – 3.0 3.0 – 3.0 = 0 Nonpolar Covalent

  23. Intermolecular Forces

  24. Intermolecular forces: attractive forces betweenmolecules. Intramolecular forces:attractive forces within a molecule (the bonds) intramolecularforces are much stronger than intermolecular forces

  25. Dipoles • What is a dipole? • A polar molecule • When there is uneven sharing of electrons so there is a separation of charge

  26. Dipole-Dipole Forces • Attraction between two polar molecules — — + +

  27. Hydrogen Bonding • Special type of Dipole – Dipole • Attraction between:Hydrogen and Nitrogen/Oxygen/Fluorine

  28. Dipole – Induced Dipole • Attraction between one polar and one nonpolar molecule — + Electrons shift toward positive end of dipole — — + +

  29. London Dispersion Forces • Attraction between two nonpolar molecules Electrons become uneven and form a dipole — — + +

  30. Strength of IMF • Hydrogen Bond • Dipole – Dipole • Dipole – Induced Dipole • London Dispersion Forces strongest weakest

  31. What does IMF effect? • Viscosity • Surface Tension • Cohesion/Adhesion • Boiling Point

  32. Viscosity • Measures a fluid’s resistance to flow Stronger IMF  Higher Viscosity

  33. Surface Tension • result of an imbalance of forces at the surface of a liquid. Stronger IMF  Higher Surface Tension

  34. Adhesion Cohesion Adhesion and Cohesion • Adhesion: intermolecular attraction between unlike molecules • Cohesion: intermolecular attraction between like molecules

  35. Boiling Point • Point at which liquid particles escape the surface of the liquid into the gas phase Stronger IMF  Higher Boiling Point

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