2012 ppt unit 2 4 covalent bonding djy r1 (draft)

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2012 ppt unit 2 4 covalent bonding djy r1 (draft)

  1. 1. Compounds and Bonding Covalent Bonding
  2. 2. Covalent bonds form between atoms ofnon-metallic elements.In a covalent bond, the octet rule issatisfied by atoms sharing electrons sothat each can have a full outer valenceshell.Shared pair of electrons formscovalent bond between hydrogenand oxygen in this water molecule
  3. 3. The number of electrons required to fill the outer shellindicates how many covalent bonds an atom can form. Forexample, to satisfy the octet rule . . Carbon will form 4 covalent bonds Nitrogen will form 3 covalent bonds Oxygen will form 2 covalent bonds Fluorine will form 1 covalent bonds Neon will form 0 covalent bonds
  4. 4. Chlorine has 7 valence electrons, and requires onemore to complete the outer shellWe know chlorine gas is a diatomic molecule and has theformula Cl2. A molecule of chlorine gas consists of twoatoms held together by a covalent bond. Shared pair of electrons (single covalent bond) Cl Cl Cl Cl
  5. 5. Try these examples. Use dot and crossdiagrams to show the covalent bonding in:HCl (hydrochloric acid) CH4 (methane) sharingStart with the Lewis dot diagrams for each element involved.Combine the diagrams to form the molecule.
  6. 6. Try these examples. Use dot and crossdiagrams to show the covalent bonding in:HCl (hydrochloric acid) CH4 (methane)In a covalent bond, the shared electrons are counted in bothatoms valence shells when applying the octet rule.
  7. 7. SimplifiedHCl (hydrochloric acid) CH4 (methane)Lewis dot structures of molecules show all the bonds (thevalence electrons)
  8. 8. Multiple covalent bondsAtoms joined by covalent bonds can sharemore than one pair of electrons. Consider amolecule of oxygen O2
  9. 9. Multiple covalent bondsTwo shared pairs = ONE double covalent bond
  10. 10. Try to draw the covalent bonding in CO2
  11. 11. Try to draw the covalent bonding in N2Three shared pairs = ONE triple covalent bond
  12. 12. Complete the bonding and naming worksheets
  13. 13. Polyatomic ionsPolyatomic ions are groups of atoms heldtogether by covalent bonds but have an overallelectrical charge -1 for example the nitrate ion NO3 -1
  14. 14. Complete the polyatomic ion worksheet (NH4)2CO3 ? Ammonium carbonate CuCl ? Copper I chloride Ca(NO3)2 ? Calcium nitrate
  15. 15. Properties of Covalent Compounds Physical Ionic Covalent Property Crystal Molecular Very highMelting and boiling Strong attractions points between ions Most ionicSolubility in water compounds are soluble in water. Yes when dissolvedConduct electricity in water or melted Hardness Very brittle Solids with Structure geometrical arrangement of ions
  16. 16. Properties of Covalent Compounds Physical Ionic Covalent Property Crystal Molecular Very high LowMelting and boiling Strong attractions Weak attractions points between ions between molecules Most ionic Only polar moleculesSolubility in water compounds are dissolve in water. soluble in water. Yes when dissolvedConduct electricity Do not conduct in water or melted Hardness Very brittle Not brittle Solids with Solid, liquid, gas Structure geometrical made of molecules arrangement of ions

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