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Lewis Structures

Lewis Structures. Lewis Structures. Covalent molecules form when two or more nonmetal atoms share valence electrons in order to complete their valence shell. Example Both hydrogen and chlorine need one extra electron to fill their valence shell. Atoms. Molecule. Lewis Structures.

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Lewis Structures

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  1. Lewis Structures

  2. Lewis Structures Covalent molecules form when two or more nonmetal atoms share valence electrons in order to complete their valence shell. Example Both hydrogen and chlorine need one extra electron to fill their valence shell. Atoms Molecule

  3. Lewis Structures In each covalent bond, two electrons are shared between the atoms. Atoms can form single, double, and triple bonds with other atoms.

  4. Lewis Structures Lewis dot structures show the location of valence electrons in covalent molecules. Remember, all elements (except for H and He) need 8 valence electrons to have a full shell. Oxygen atoms can either form a double bond or two single bonds to fill its valence shell.

  5. Lewis Structures Example – Drawing the Lewis dot structure for NH3 1. Draw the electron dot structure of each atom.

  6. Lewis Structures 2. Match up all unpaired electrons. (You can move them to different sides, even multiple unpaired electrons to the same side)

  7. Lewis Structures 3. Make sure each atom has a full valence shell. (2 electrons for hydrogen, 8 electrons for all other atoms)

  8. Lewis Structures Covalent molecules are most often drawn using structural formulas. Single lines are used to represent each pair of bonding electrons. Lewis Dot Structure Structural Formula

  9. Lewis Structures Examples

  10. Lewis Structures Remember HONC – 1, 2, 3, 4

  11. Lewis Structures Example – Drawing the structural formula for C2H4 1. Determine the number of bonds each atom needs.

  12. Lewis Structures 2. Draw a simplified structure of the molecule, placing the atoms that need the most bonds at the center of the molecule.

  13. Lewis Structures 3. Add in double/triple bonds where needed so that each atom has the necessary number of bonds.

  14. Lewis Structures When multiple structures exist for a single chemical formula, they are called isomers. C2H6O

  15. Lewis Structures Not all covalent compounds are electrically neutral. Polyatomic ions are charged covalent compounds. Example – Hydroxide (OH‒) The extra electron gives hydroxide its negative charge

  16. Lewis Structures The six polyatomic ions below are some of the more common polyatomic ions. These should be memorized.

  17. Lewis Structures The Lewis dot structure for polyatomic ions should give each atom a full valence shell, and must match the charge of the ion. Examples – Carbonate (CO32‒) and Ammonia (NH4+)

  18. Lewis Structures 1. In covalent bonds, the electrons are… • Transferred from one atom to another • Converted into neutrons • Free to move from atom to atom • Shared between two atoms

  19. Lewis Structures 2. Which element needs two covalent bonds to complete its valence shell? • Hydrogen • Oxygen • Phosphorus • Carbon

  20. Lewis Structures 3. Which chemical below is not formed with covalent bonds? • SF2 • H2S • HNO • NaF

  21. Lewis Structures 4. Draw the Lewis dot structure for SBr2. Br S Br

  22. Lewis Structures 5. Which structure below correctly shows how carbon and hydrogen bond to form a compound?

  23. Polyatomic Ions 6. What is the formula for hydroxide? • HO3‒ • H2O‒ • OH4‒ • OH‒

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