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Covalent Bonding

Covalent Bonding. Covalent Bonding. A covalent bond is when valence electrons are shared between two atoms with high electronegativity ( nonmetals) . A molecule is a neutral group of atoms held together by covalent bonds.

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Covalent Bonding

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  1. Covalent Bonding

  2. Covalent Bonding • A covalent bond is when valence electrons are shared between two atoms with high electronegativity (nonmetals). • A molecule is a neutral group of atoms held together by covalent bonds. • A molecular or covalent compound is a compound made up of nonmetals that are covalently bonded.

  3. Covalent Bonds (cont) • Two atoms held together by sharing a pair of electrons are joined by a single covalent bond so that both atoms have a full valence shell like a noble gas!

  4. Covalent Bonds (cont) • Single bond: One shared pair of electrons • Double bond: Two shared pairs • Triple bond: Three shared pairs • Double and triple bonds form when an atom needs to share additional electron pairs to become like a noble gas • Triple bonds are the strongest and the shortest • http://www.tutorvista.com/content/chemistry/chemistry-i/chemical-bonding/covalent-bond-animation.php

  5. http://www.youtube.com/watch?v=QqjcCvzWwww • http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/atomic/covalentrev1.shtml • http://www.youtube.com/watch?v=y2uUl7fyPBM

  6. Molecular Compounds • Properties of molecular compounds: • Low melting and boiling points • Are softer than ionic compounds • Insoluble or very low solubility in water (don’t dissolve well) • Do not conduct electricity in solution • Smells

  7. Formulas • Molecular compounds can have their formula written out two different ways: molecular and structural • Molecular formulas are chemical formulas for molecules and show what atoms make up a molecule and how many of each there are. • Ex: CO2 • Structural formulas show how the atoms are bonded and are done using Lewis structures. two oxygens one carbon

  8. Strategy for drawing Lewis Structures: Step #1 • Look up valence number for each atom and add them up • Carbon dioxide (CO2) C  4 O 6 x 2 = 12 16 Total Electrons

  9. O C O Step #2 • Start by adding single bonds between atoms • single bonds = 2 e- • The least electronegative element goes in the center • Except C always goes in the center and H never does.

  10. O C O Step #3 • Add electron dots around the atoms IN PAIRS until there are the number of valence electrons you calculated in step #1. • Bond lines count as 2 electrons • NOTE: Hydrogen only wants 2 max Boron usually only wants 6

  11. O C O Step #4 • Add up electrons around each atom and see if they have a full octet. • If the all have a full valence shell, you are done! • If they don’t, move on to step #5. • The C has 8 and is full. Each O has only 6. So we must move on to the next step.

  12. O C O Step #5 Try a double bond • Next try moving pairs of e- to create double bonds: • Unshared pair are electrons that are not involved in a bond Unshared pair of electrons

  13. HONC rule • HONC is a way to remember how many bonds each type of atoms usually needs based on unpaired electrons • Hydrogen – 1 bond, no unshared pairs • Oxygen -2 bonds, 2 unshared pairs • Nitrogen -3 bonds, 1 unshared pair • Carbon- 4 bonds, no unshared pairs. • Try CH2O on your own...

  14. Lewis Structures • Draw Lewis structures for the following: • H2O • PH3 • CCl2H2 • C2H4 • OH- • NO2- • NH4+

  15. Naming Covalent Compounds • Use prefixes to determine how many of each type of atom • If first prefix is mono, leave it off • The last element listed ends in -ide

  16. Naming Covalent Compounds (cont) • Name the following • CO • SiO2 • N2O • P2O4 • SI2 • ClF • CCl2H2 • C2H4

  17. Naming Covalent Compounds (cont) • Write the formulas for the following: • Octacarbon octahydride • Diphosphorous trinitride • Carbon disulfide • Bromine monofluoride

  18. Chapter 8 Section 2 Chemistry

  19. Types of Covalent Bonds • There are two types of covalent bonds: polar and nonpolar • The different types exist because atoms do not share electrons equally • When electrons are shared equally it is a nonpolar bond • When electrons are not shared equally it is a polar bond

  20. Electronegativity • What determines if electrons are shared equally? • Electronegativity which is the ability to attract electrons in a chemical bond • The greater the difference in electronegativity the more polar the bond becomes • p 285 has the table of electronegativity

  21. Polar or Nonpolar? (cont)

  22. Polar or Nonpolar? • Identify if the following are polar or nonpolar • H-H • O-H • P-Cl • F-N • Br-I

  23. Polar Bonds • In polar bonds the electrons spend more time on the more electronegative element because it is “hogging” the electrons • Cl is the more electronegative so the electrons spend more time with it

  24. Polar Bonds • What is going to happen to the charges of the atoms in a polar bond? • The more electronegative will gain a partial negative charge and the least electronegative will have a partial positive charge • The partial charge can be shown with a Greek symbol () delta or special arrows

  25. Polar Bonds (cont) Positive Negative

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