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I. Covalent Bonds

Covalent bonds form between atoms sharing electrons. Different types of bonds include single, double, and triple bonds, each involving specific electron sharing. This guide explains bond formation, reviews ionic vs. covalent compounds, and details bond polarity.

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I. Covalent Bonds

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  1. I. Covalent Bonds A. These bonds are formed from twoatoms _________ electrons, so each atom will have a filled outer energy level. sharing 1 dash represents 2 electrons A bond is drawn as a dash:  This is called a Structural Formula B. Three types of bonds can be formed: 1 pair of electrons are shared between 2 atoms, 2e- total Single - 2 pairs of electrons are shared between 2 atoms, 4e- total Double - 3 pairs of electrons are shared between 2 atoms, 6e- total Triple -

  2. II. Bond Formation A. Covalent bonds are formed from two or more ______________ ONLY, which are found in groups: nonmetals 4A-7A • The sharing of e- will allow each atom to achieve a stable noble gas e- configuration. • Each atom will have 8 valence electrons or a full octet creating filled orbitals. Exception: Cl Cl H H Stable configuration Circle the shared electrons

  3. III. Review Ionic Compounds vs. Covalent Compounds Ionic Bonds Covalent Bonds Anion & cation 2 or more nonmetals Transfer e-: Arrow is used Share e-: Circle the e- shared between the2 atoms Chemical Formula = Formula Unit Chemical Formula = Molecular formula A line is notused to represent a bond, why? A line is used to represent a bond, why? Share e- Don’t share e-

  4. Covalent Bonds two atoms share e- One pair of electrons Two pairs of electrons Three pairs of electrons called called called Single bond Double bond Triple bond Drawing covalent molecules takes practice & patience! Practice makes perfect!

  5. Bond Polarity Bond Polarity pairs of electrons may not be shared equally. greater electronegativity greater attraction/bonding e- to itself. Bond type found by difference in electronegativity subtract the two numbers. 3 types of bonds.

  6. CovalentPolar Microwavid. Covalent Nonpolar Ionic 0 - 0.49 0.50 – 1.9 2.0+ sharedequally not sharedat all! sharedunequally

  7. CH4 Methane C H 2.5 2.1 = 0.4 The atom that is more electronegative (stronger attraction of e-) acquires a semi-negativecharge & the less electronegative acquires a semi-positive charge. A delta symbol is used to showthe attraction. C Br = 0.3 2.8 2.5

  8. Electronegativity

  9. Electronegativity

  10. HCl Hydrochloric A. Cl H = 0.9 3.0 2.1 Arrow points to the more electronegative element. The bonding electrons are displaced more towards the atom with the higher electronegativity. C F 4.0 = 1.5 2.5

  11. The more electronegative element, Cl, attracts the bonding electrons more.

  12. Example - Ionic Na+ Cl- = NaCl 0.9 3.0 = 2.1 The electrons are not shared between the two atoms but they are: Transferred Therefore:arrows & partial charges are not drawn because the e- are NOTshared. = K2O K+ O2- 0.8 3.5 = 2.7

  13. More Examples: NH4 ammonia N H = 0.9 3.0 2.1 F F 4.0 4.0 = 0.0 Why is an electronegativity arrow not drawn over F2? It is a non-polar bond!

  14. Reading Quiz 16-2 1. When atoms in a molecule equally share electrons, the bond formed is ____________. 2. Unequally shared electrons are found in __________ bonds. 3. The bond type can be found by subtracting the two atom’s _____________ numbers. 4. In a polar molecule, one end of the molecule is slightly __________ and the other end is slightly __________. 5. A molecule that has two poles is called a _____.

  15. DRAWING COVALENT LEWIS DOT STRUCTURES RULE 1 “ C N O F” RULE 2 4 3 2 1 # BONDS RULE 3 ADD enough valenc e- RULE 4 ADD/SUBT e’s for +/- pos ions LETS TRY H2O NH4+ CO32- FCN F2 H2 N2 CN-

  16. O C O H H Draw the structural formula for HCOOH, with electronegativity numbers and arrows.

  17. CH2O NOH H2S CH3Cl CH4 H2O2 H2SO4 CF4 CBr2H2 CH3NH2 HCl CO SO3 Exceptions Odd # valence NO2

  18. ■Acetic acid C2H3O2 ■Acetone ■Acetylene C2H2 ■Carbon tetrachloride CCl4 ■Hexane C6H14 ■Carbonic acid H2CO3 ■Dichloro-difluoro-methane C2Cl2F2 ■1,2-Dichloroethane C2H4Cl2 ■Dichloro-difluoro-methane CF2Cl2 ■Dimethyl sulfide CH3SCH3 ■Ethane C2H6 ■Ethanol C2H5 ■Ethene C2H4 ■butane C4H10 ■propanol C3H7OH ■Methanol CH3OH ■Pentane C5H12 ■Propane C3H8 ■Propionic acid C3H5O2H ■Propyne C3H4 OH

  19. Exceptions to the Rules Odd # valence NO2 Incomplete octets MgH2 LiH AlH3 BF3 Expanded Octets SF6 PCl5 XeF4 SeF4 Resonance O3

  20. Molecular Polarity Molecular Polarity Definition: Dipole - A molecule that has 2 poles, one end is partially (+), the other end is partially (-). Must know:1 - bond polarity & 2 - molecular shape (VSEPR)to predict molecule polarity!

  21. Molecular Polarity Definition - Polar Molecule 1. Must have at least 1 polar bond.This is required! 2. Most molecules with lone pairs on the central atom are polar! ex: bent &pyramidal 3. Tetrahedral shape must be unsymmetrical 105o ex: CH3Cl Different atoms bonded to the central atom.

  22. Molecular Polarity Definition - Nonpolar Molecule 1. May have polar bonds.(not required) 2. Molecules with nolone pairs on the central atom are usually nonpolar. ex: trigonal planar & linear 3. Tetrahedral shape must be symmetrical! ex: CH4, CF4 (all atoms bonded to the central atom are the same)

  23. Example 1 Electronegativity difference O-H:3.5 - 2.1 = 1.4 Bond polar or nonpolar? O 3.5 H H 2.1 2.1 Draw the structural formula for H2O Polar or Nonpolar Molecule Why??

  24. Example 2 2.5 3.5 3.5 C O O Electronegativity difference O-C:3.5-2.5 = 1.0 Bond polar or nonpolar? Draw the structural formula for CO2 Polar or Nonpolar Molecule Why??

  25. Molecule of Butane Carbon Hydrogen

  26. Example 3 Electronegativity difference Cl-C:3.0-2.5 = 0.5 3.0 Cl Bond polar or nonpolar? 2.5 Bond polar or nonpolar? C H H 2.1 2.1 H Electronegativity difference C-H:2.5-2.1 = 0.4 2.1 Draw the structural formula for CH3Cl Polar or Nonpolar Molecule Why??

  27. Example 4 2.1 H Electronegativity difference C-H: 2.5 - 2.1 = 0.4 2.5 C Bond polar or nonpolar? H H H Why?? Draw the structural formula for CH4 Polar or Nonpolar Molecule

  28. Example 5 Electronegativity difference P-H:2.1-2.1 = 0 2.1 Bond polar or nonpolar? P H H H 2.1 Draw the structural formula for PH3 Polar or Nonpolar Molecule Why??

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