1. I. Introduction to Bonding
Ch. 7 & 8 - Chemical Bonding

2. Lewis (Electron) Dot Structures
Lewis Structure: atoms represented using the element symbol and dots for valence electrons
Two shared e- equals one bond
e- not used to form a bond are called “lone pairs” or “nonbonding pairs”
Cations (positive ions) have Lewis structures without valence electrons
Anions (negative ions) have Lewis structures with 8 valence electrons

3. A. Types of Bonds IONIC COVALENT
Bond Formation
e- are transferred from metal to nonmetal
Type of Structure
crystal lattice
Physical
State
solid
Melting
Point
high
Solubility in
Water
yes
Electrical Conductivity
yes (solution or liquid)
Other
Properties

4. Ionic Bonding
Ionic Bond: a total transfer of one or more electrons from one atom to another
Ionic compounds form into crystals of repeating formula units
Ionic bonds are extremely strong
Reactions between metals and nonmetals (representative) tend to form ionic bonds
A positively charged ion (CATION) is attracted to a negatively charged ion (ANION)—attraction between ions is due to their opposite charges
Example: Na+ + Cl-  NaCl

5. Ionic Compounds (Salts)
Composed entirely of ions
Electrically neutral (Ex: Al3+ and N3- combine to form AlN)
Properties:
Crystal lattice (geometric pattern)
High melting points (solids at room temp.)
Brittle and hard
Liquid (molten) state conducts electricity; solid state does not
Solutions are good conductors

6. B. Vocabulary
Chemical Bond: the force of attraction between nuclei and valence electrons of neighboring atoms that binds the atoms together
Interactions involving valence electrons are responsible for the chemical bond (only valence electrons are transferred or shared in chemical reactions)
Valence electrons are outermost s and p sublevels
bonds form in order to…
decrease PE
increase stability

7. Na+ NO3- ION B. Vocabulary 1 atom 2 or more atoms Monatomic Ion
Polyatomic
Ion
Na+
NO3-

8. NaCl NaNO3 COMPOUND B. Vocabulary more than 2 elements 2 elements
Binary
Compound
Ternary
Compound
NaCl
NaNO3

9. In an IONIC bond, electrons are lost or gained,resulting in the formation of IONS in ionic compounds. F K

10. K F

11. K F

12. K F

13. + _ K F

14. K F _ The compound potassium fluoride consists of potassium (K+) ions
and fluoride (F-) ions

15. A. Types of Bonds METALLIC e- are delocalized among metal atoms
Bond Formation
Type of Structure
“electron sea”
Physical
State
solid
Melting
Point
very high
Solubility in
Water no
Electrical Conductivity
yes (any form)
malleable, ductile, lustrous
Other
Properties

16. Metallic Bonding - “Electron Sea”
A. Types of Bonds
Metallic Bonding - “Electron Sea”

17. Covalent Bonding - True Molecules
A. Types of Bonds
Covalent Bonding - True Molecules
Diatomic Molecule

18. But rather than losing or gaining electrons, atoms now share
In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule).
But rather than losing
or gaining electrons,
atoms now share
an electron pair.

19. Covalent Bonding
Covalent Bond: attractive forces due to the sharing of electrons between atoms
A group of covalently bonded atoms (with no overall charge) is called a molecule

20. Covalent Bonds
Result from sharing of electrons (so that all atoms have filled outer energy levels  stable)
In addition to hydrogen, atoms in Groups 4A, 5A, 6A, & 7A often form covalent bonds.
Covalent compounds can contain single, double or triple bonds between atoms
Single covalent bond: formed by a shared pair of electrons between two atoms
Bond strength increases as the number of bonds between the atoms increases

21. Cl Cl

22. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle
circle the electrons for
each atom that completes
their octets

23. Cl Cl
This is the bonding pair

24. Cl Cl It is called a SINGLE BOND circle the electrons for
each atom that completes
their octets

25. Single bonds are abbreviated with a dash
Cl - Cl
Single bonds are abbreviated with a dash

26. O
How will two oxygen atoms bond?

27. O
Each atom has two unpaired electrons

28. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

29. O O

30. O O
two bonding pairs,
making a double bond

31. O O =
For convenience, the double bond
can be shown as two dashes.

32. NaCl CO2 CHEMICAL FORMULA B. Vocabulary IONIC COVALENT Formula Unit
Molecular
Formula
NaCl
Sodium chloride
CO2
Carbon dioxide

33. A. Types of Bonds IONIC COVALENT
Bond Formation
e- are transferred from metal to nonmetal
e- are shared between two nonmetals
Type of Structure
crystal lattice
true molecules
Physical
State
solid
liquid or gas
Melting
Point
high
low
Solubility in
Water
yes
usually not
Electrical Conductivity
yes (solution or liquid) no
Other
Properties

34. Diatomic Molecules: occur in pairs
Remember: atoms are electrically neutral (not like an ion)
Why share? to acquire stable electron configurations
What is a molecule? Group of atoms held together by covalent bonds. Covalent compounds are molecular compounds.
Diatomic Molecules: occur in pairs
Super Seven (ClIF H BrON) YEP: MEMORIZE!
(Halogens form single covalent bonds in their diatomic molecules).

35. Types of Formulas
Empirical Formula: Shows the relative numbers of atoms in a compound (ratio of atoms to each other)
Molecular Formula: Shows the exact formula of the compound (the number of atoms of each element in the compound)
Structural Formula: Identifies which atoms are bonded to which in a molecule
Dashes (in structural formulas) indicate a pair of shared electrons (dashes are NEVER used to show ionic bonds)

36. C. Bond Polarity
Most bonds are a blend of ionic and covalent characteristics.

37. C. Bond Polarity Nonpolar Covalent Bond e- are shared equally
symmetrical e- density
usually identical atoms

38. + - C. Bond Polarity Polar Covalent Bond e- are shared unequally
asymmetrical e- density
results in partial charges (dipole) + -

39. C. Bond Polarity
Nonpolar
Polar
Ionic

40. C. Bond Polarity Electronegativity
Attraction an atom has for a shared pair of electrons.
higher e-neg atom  -
lower e-neg atom +

41. C. Bond Polarity Electronegativity Trend
Increases up and to the right.

42. C. Bond Polarity ionic: electronegativity difference  2
Electronegativity differences used to predict polarity of a bond.
ionic: electronegativity difference  2
polar covalent: electronegativity difference
nonpolar covalent: electronegativity difference  0.5

43. Which one of these bonds would be least polar? B-C C-N B-Si
Boron:
Carbon: 2.55
Nitrogen:3.04
Silicon: