1. A. Types of Chemical Bonds
Ch12 Chemical Bonding
A. Types of Chemical Bonds
Bond – force that holds groups of atoms together and makes them function as a unit
Bond energy – energy required to break a chemical bond

2. Ionic Bonding
(b)
(a)
Ionic compound results when a metal reacts with a nonmetal

4. Covalent Bonding
A covalent bond results when electrons are shared by nuclei

5. Covalent Bonding (continued)
A polar covalent bond results when electrons are shared unequally by nuclei
One atom attracts the electrons more than the other atom

7. B. Electronegativity
Electronegativity – the relative ability of an atom in a molecule to attract shared electrons to itself
Increases from left to right across a period
Decreases down a group of representative elements

8. The polarity of a bond depends on the difference between the electronegativity values of the atoms forming the bond

9. C. Bond Polarity and Dipole Moments
A dipole moment results when a polar molecule has a center for positive charge separate from a center for negative charge

10. Water molecule dipole moment

11. The polarity of water affects its properties
Permits ionic compounds to dissolve in it
Causes water to remain liquid at higher temperature

12. D. Stable Electron Configurations and Charges on Ions

14. Atoms in stable compounds usually have a noble gas electron configuration
Metals lose electrons to reach noble gas configuration
Nonmetals gain electrons to reach noble gas configuration

15. Predicting Formulas of Ionic compounds
Chemical compounds are always electrically neutral

16. E. Ionic bonding and Structures of Ionic Compounds
Ions are packed together to maximize the attractions between ions

17. Structures of Ionic Compounds
Cations are always smaller than the parent atom
Anions are always larger than the parent atom

18. Ionic Compounds Containing Polyatomic Ions
Polyatomic ions work in the same way as simple ions
The covalent bonds hold the polyatomic ion together so it behaves as a unit

19. F. Writing Lewis Structures
In writing Lewis structures we include only the valence electrons
Most important requirement
Atoms achieve noble gas electron configuration (octet rule, duet rule)

20. Bonding pairs are shared between 2 atoms
Unshared pairs (lone pairs) are not shared and not involved in bonding

21. Rules for Covalent Bonds
1. Determine the total number of valence electrons
2. Write the skeleton structure and join the atoms in
this structure by single covalent bonds
3. For each single bond formed, subtract 2 from the
total number of valence electrons
4. With the remaining valence electrons first complete
the octet (or duet) of the outside atoms, then complete
the octet of inner atoms
5. If the inner atom lacks an octet, form multiple bonds
by sharing more electrons from outer atoms to inner atoms
Double bond 2 pair e-
Triple bond  3 pair e-

23. G. Lewis Structures of Molecules with Multiple Bonds
Single bond – covalent bond in which 1 pair of electrons is shared by 2 atoms
Double bond – covalent bond in which 2 pairs of electrons are shared by 2 atoms
Triple bond – covalent bond in which 3 pairs of electrons are shared by 2 atoms

24. A molecule shows resonance when more than one Lewis structure can be drawn for the molecule

25. H. Molecular Structure
Three dimensional arrangement of the atoms in a molecule
Water - bent

26. Linear structure – atoms in a line
Carbon dioxide

27. Trigonal planar – atoms in a triangle
BF3

28. Tetrahedral structure
methane

29. I. The VSEPR Model Valence shell electron pair repulsion (VSEPR) model
Molecular structure is determined by minimizing repulsions between electron pairs

30. Two Pairs of Electrons
BeCl2
180o - linear

31. Three Pairs of Electrons
BF3
120o – trigonal planar

32. Four Pairs of Electrons
CH4
120o – tetrahedral

35. J. Molecules with Double Bonds
When using VSEPR model to predict molecular geometry of a molecule
a double bond is counted the same as a single electron pair