1. Covalent Bonding Between nonmetal atoms
Share valence electrons between atoms
Electron clouds overlap
Ex: H2O
CH4
NH3
CO2

3. Electronegativity
Difference in EN smaller than in ionics and is usually < 1.7
Ex: HCl
H = 2.2 Cl = 3.2
Difference = 1.0

4. Bond Polarity Polar Bonds:
Have a difference in EN values (unequal sharing)
Ex: H Cl
EN= EN=3.2

5. NonPolar Bond: no difference in EN values. (equal sharing)

6. Comparing Bond Types

7. Single, Double, Triple Bonds
Atoms can share single double or triple bonds between them.
Each bond represents a shared pair of electrons.
3 pair here = 6 electrons!

9. Molecular Formulas Covalent compounds are molecules.
Made up of all nonmetals.
Molecular formulas: show actual number of atoms of each element present
Ex: H2O
2 hydrogen atoms, 1 oxygen atom

10. Ionic Compounds (SALTS)
formula unit indicates simplest ratio of ions in the crystal structure
Covalent Compounds (MOLECULES)
molecular formula indicates actual number of atoms present in molecule
NaCl = 1:1 ion ratio
CH4 = 5 atoms in molecule
Formula Units vs. Molecules 7 minutes

11. Structural Formulas of Molecules
Show how the atoms are bonded together
Use “lines” to show covalent bonds
Dots show free electron pairs

12. Empirical Formulas
Show simplest whole number ratio of atoms or ions in the compound.
Ex: MgCl2 1 : 2 ion ratio
Al2(SO4)3 2 : 3 ion ratio
NOTE:
All ionic compounds have empirical formulas

13. You can simplify some molecular formulas to make them empirical ratios
Ex: C6H12O6
Simplest ratio of atoms ___________
C6H6
CO2

14. Naming Binary Covalent Compounds
Prefix system indicates number of atoms
Add “-ide” ending

15. Examples of Naming Covalents
Note: use “mono” prefix if only one of 2nd element.

17. Drawing Covalent Molecules
Lewis Structures

18. STEPS TO DRAW MOLECULE Count total valence e- in the molecule
Draw molecule with single bonds between atoms then subtract these e- from total
Evenly distribute remaining e- in pairs to all atoms in molecule that still need e-
Check to see if all obey octet rule (Hydrogen is 2 e-)
If deficient, shift over free e- pairs to make double or triple bonds as needed.

19. Draw NH3
Draw H2O
Draw CH4

20. Crash Course Chemistry: Lewis Structures: (11 minutes)

21. Drawing Polyatomic Ions
Covalently bonded atoms with a group charge
Add or subtract electrons from total valence depending on charge.
Draw brackets around ion and indicate charge.
Ex: (SO4) -2
6 + 4(6) + 2 = 32 electrons

22. VSEPR and Molecular Shape
Assume valence electrons repel each other.
Molecule adopts 3D geometry that minimizes this repulsion.
Valence Shell Electron Pair Repulsion (VSEPR) theory.

23. Predicting Molecular Geometries
Draw Lewis structure
Count total number of electron pairs around the central atom (both shared and unshared)
Arrange electron pairs to minimize e-repulsion
Multiple bounds count as one bonding pair

24. Molecular Shapes Regents Shapes to Know: Tetrahedral Pyramidal Bent
Linear

25. Is a Molecule Polar?
If the centers of negative and positive charge do not coincide, then the molecule is polar.

26. Look for Symmetry Polar Molecules: Nonpolar Molecules OR
Have polar bonds and are not symmetrical
Positive & negative “partial charges” don’t overlap
They have a “dipole moment”
Nonpolar Molecules
Have nonpolar bonds OR
Have polar bonds and are symmetrical
Centers of positive & negative charge overlap

27. Example:
In CO2, the polarity of each C-O bond is cancelled because the molecule is linear.
In H2O, the polar H-O bonds do not cancel because the molecule is bent.

28. Tetrahedral
Has 4 atoms bonded (no free pairs)

29. Symmetry? Depends on what atoms are attached.
Can be polar (asymmetrical)
or nonpolar (symmetrical)

30. Pyramidal
Three atoms bonded (one free pair)

31. All pyramids are asymmetrical.
These molecules are always POLAR!

32. Two atoms attached (2 free pair)
Bent
Two atoms attached (2 free pair)
The 2 free pair make it bent and not linear.
These are always asymmetrical so are always polar.
H2O

33. Hey, Water is Polar!!!!!
Never forget this!!!

34. Linear: 2 or 3 atoms in a line
Can be polar or nonpolar depending on type of bonding and symmetry
EX: Cl2, O2, N2, HCl, CO2

35. Ex: Linear Symmetrical Molecules

36. Properties of Covalent Compounds Note: These properties can vary depending on if molecule is polar or not!

37. Melting Point Lower than Ionics
To melt, you are only separating the weak bonds between molecules (not within).

38. Melting Point Polar Molecules (dipoles/”mini-magnets”):
Have higher melting points than non-polars because they are harder to separate.

39. All these nonpolar diatomics have really low MP/BP

40. Solubility “Like Dissolves Like”
Polar Molecules dissolve in polar solvents as they are attracted to them
like H2O, CHCl3, NH3 etc.
Non-polar Molecules dissolve in non-polar solvents
like hexane, CCl4

41. Oil and water don’t mix!
How does soap work?

42. Conductivity
Covalent Molecules do not conduct well as they do not form ions.
They are “nonelectrolytes”
Except Acids!!!!
Acids are covalently bonded but in water (aqueous) they will ionize and conduct current.
(Acids are not on this test)

43. Decompose
If the heat gets high enough covalent compounds will break down and decompose.
(Remember the lab, sugar melted first, then it burned and turned into black carbon)

44. Other Types of Covalent Bonds

45. Coordinate Covalent Bonding
Covalent bond in which one of the bonding atoms donates both of the electrons to the bond.
The other atom donates nothing.
Ex: Forming Hydronium Ion

46. H+1 To form this type of bond you must have:
A molecule with a free pair of electrons
Something that needs to gain 2 electrons
H+1

47. Ex: Forming Ammonium Ion

48. Network Solids Giant network of covalently bonded atoms.
Large macromolecules
Extremely strong structures
Unusually high M.P.
Do not dissolve
Diamonds are a giant network of carbon atoms.

49. Ex: C (s) (graphite, diamond, buckyball), SiO2 (quartz), GeO2

50. Bonding in Pure Metals
Hunting the elements:

51. Metallic Bonding Happens in pure metals or alloys.
Ex: Mg, Fe, Brass, Au, Ni, Cu
“Delocalized” valence electrons move about between all the metal atoms.

53. Metallic Bonding Properties Conducts heat and electricity very well
Conducts as a solid too!
Does not dissolve in solvents
Malleable and Ductile
Relatively high melting point.
Higher MP than covalents.
Similar MP to most ionics
(4:30)
(4:13)
Properties 2:00:
What is a metal? 4:30

54. Metallic Bonding

55. Comparing Properties Melting Point/Boiling Point Conductivity
Solubility

57. EXTRA VIDEO LINKS FOR FUN AND LEARNING
Ionic vs. Covalent Bonding
Electronegativity
Bonding Dance Party
It’s a chemical bond baby”
Dancin Queen (Ionic/Covalent Bonds)
Isn’t it Ionic
Dogs teaching Chem (Ionic vs. Covalent Bonds (2 min)

58. GOOD FOR REVIEW Crash Course Chemistry: Polarity of Molecules
Dipole Moment:

59. Types of Chemical Formulas Tutorial
Naming Tutorial (Ionic & Covalent)
Writing Formulas Tutorial (Ionic & Covalent)