Molecular compounds - Ms. Goldenberg

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Molecular compounds - Ms. Goldenberg

  1. 1. Molecular Compounds
  2. 2. Molecular Compounds Molecule: Combination of two or more atoms held together by covalent bonds Covalent bonds: When two non-metal atoms share electrons
  3. 3. Diatomic Molecules  Diatomic molecule: When two atoms of the same elements are joined by covalent bonds (Cl2, Br2, HF)
  4. 4. Molecular Compounds Molecular Compound: When two or more different non-metals come ogether and share electrons to form covalent bonds.  In each bond, the atoms share a single pair of electrons.
  5. 5. Molecular Compounds  For example, water is a molecular compound with two covalent bonds  Each hydrogen atom shares one pair of electrons with an oxygen atom
  6. 6. Properties of Molecular Compounds    soft low melting point solutions do not conduct electricity
  7. 7. Naming Molecular Compounds 1.Name the first element 2.Name the second element and change the ending to “-ide” 3.Add prefixes to indicate the number of each atom
  8. 8. Naming Molecular Compounds Example 1: N2O
  9. 9. Naming Molecular Compounds The prefix “mono” is not used when there is only one atom of the first element When two vowels are next to each other, drop the vowel in the prefix e.g. “monoxide” not “monooxide” e.g. “pentoxide” not “pentaoxide”
  10. 10. Naming Molecular Compounds Example 2: PBr3
  11. 11. Naming Molecular Compounds Name the following molecular compounds:  PCl3  AS3P5  diphosphorous pentoxide  carbon disulfide
  12. 12. Naming Molecular Compounds  Many compounds containing hydrogen have been given simpler names  For example, dihydrogen monoxide (H2O) is simply called “water”
  13. 13. Naming Molecular Compounds
  14. 14. Molecular Compound Diagrams  Lewis Dot Diagram  Structural  Line Diagram Diagram (MaCS)
  15. 15. Lewis Dot Diagram  only valence electrons are shown  only UNPAIRED ELECTRONS can be shared  Arrangements of electrons around the element name must take on the same orientation as if there was an imaginary orbital ring around the atoms WRONG WAY H .. H H : H RIGHT WAY H:H H .. H
  16. 16. Lewis Dot Diagram  Draw Lewis dot diagrams for the following examples on your worksheet:  H2O  CO2  NH3  CH4
  17. 17. Drawing Molecular Compounds  Lewis diagrams can be quite time consuming and is difficult to read and thus most textbooks use alternate forms of representation:  Structural diagrams  Line diagrams
  18. 18. Structural Diagram  Each pair of shared electrons is replaced with a single line segment connecting the two atoms   Each single line represents a bond If two atoms share 4 electrons (2 pairs), then you would use 2 line segments (like an equal sign) representing double bonds  Lone pairs of electrons (electron pairs that are not shared) are NOT shown
  19. 19. Lewis Dot Diagram  Draw Lewis dot diagrams Structural diagrams for the following examples on your worksheet:  H2O  CO2  NH3  CH4
  20. 20. Structural Diagram  Practice: translate this Lewis Dot diagram into a structural diagram
  21. 21. Summary Atom H O N C # of valence electrons # of unpaired electrons (can be shared) # of bonds
  22. 22. Summary Atom H O N C # of valence electrons # of unpaired electrons (can be shared) # of bonds 1 1 1 6 2 2 5 3 3 4 4 4
  23. 23. Molecular Compound Diagrams  Lewis Dot Diagram  Structural  Line Diagram Diagram (MaCS)

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