1. Unit 6: Molecular Compounds

2. Atoms
Monatomic = 1 atom

3. Molecules
Molecule =
2 or more nonmetal
atoms acting as a
unit

4. Diatomic = molecules of 2 of the same atoms

5. Low melting and boiling points Do not conduct electricity in H2O
Molecular Compounds
Composed of molecules
Low melting and boiling points
Do not conduct electricity in H2O
Gases or liquids at room temp
2 or more different nonmetals

6. Molecular Compounds
Prefix system used

7. Molecular Compounds
Prefix system used

8. Molecular Compounds Prefix1element1 prefix2element2 + -ide
Except mono is never used on element1

9. Acids – 6 common Acids?

10. Common Acids Formula Name HCl hydrochloric acid HNO3 nitric acid
H2SO4 sulfuric acid
H2CO3 carbonic acid
H3PO4 phosphoric acid
HC2H3O2 acetic acid

11. electrons are shared between nonmetals in groups 4A,5A,6A,7A
Covalent Bonding
electrons are shared between nonmetals in groups 4A,5A,6A,7A

12. Rules for drawing Lewis structures
Covalent Bonding
Rules for drawing Lewis structures
1. Add valence electrons for all atoms

13. 2. Write symbols for atoms to show arrangement of atoms
Covalent Bonding
2. Write symbols for atoms to show arrangement of atoms
C is always in the middle
H is always outside
Least electronegative atom is in the middle

14. 3. Complete the octets of atoms bonded to central atom, except H
Covalent Bonding
3. Complete the octets of atoms bonded to central atom, except H
4. Place leftover electrons on central atom
5. If central atom is incomplete try a multiple bond

15. Single Covalent Bonding
bond in which two atoms share a pair of electrons
Ex] H2

16. Single Covalent Bonding
Structural Formulas - a shared pair of electrons are represented by a dash

17. Single Covalent Bonding
Examples:
Fluorine
Dihydrogen monoxide
Ammonia
Carbon tetrachloride
Phosphorous tribromide

18. Double and Triple Covalent Bonding
Double bonds:
share 2 pairs of electrons, (=)
Triple bonds:
share 3 pairs of electrons
Examples:
Nitrogen
Carbon dioxide

19. Practice – Draw Lewis Structures
Br2
SiCl4
HCl O2
HCN CO

20. Resonance Structures
structures that occur when it is possible to write 2 or more valid lewis structures that have the same number of electron pairs for a molecule or ion
Example - O3

21. Polyatomic Ions
covalently bonded
Examples:
NH4+
SO32-
ClO3-

22. Exceptions to the Octet Rule
Some substances do not obey the octet rule and can have an incomplete or expanded octet
Examples: BF3, PCl5, SF6, XeF4

23. Practice – Draw Lewis Structures
SO2
SO42-
H3O+
OH-
BH3
XeF2
H2O2
NCl3
NO3-

24. Molecular Geometry
Shape of a molecule is determined by the bond angle which is based on the number of electron domains in the molecule

25. Molecular Geometry
A pair of electrons, single, double, and triple bonds each consist of 1 electron domain

26. 1. Draw Lewis structure and count e-d’s
Molecular Geometry
To Predict Shapes:
1. Draw Lewis structure and count e-d’s
2. Predict bond angles and molecular geometry using table

27. Molecular Geometry

29. Molecular Geometry
Examples:
CO2
BF3
CBr4
PCl5
SF6

30. Molecular Geometry Practice: Predict Shape and Angle BeF2 BCl3 SiH4
AsF5
NO3-
ClO4-

31. Intramolecular vs. Intermolecular
Intramolecular Forces – forces within molecules – chemical bonds (ionic and covalent bonds)
Intermolecular Forces (IMF’s) – forces between molecules – dispersion, dipole-dipole, hydrogen bonding

32. Intermolecular Forces
Broken during phase change
The stronger the IMF, the higher the mp/bp

33. Types of Intermolecular forces
London Dispersion forces:
All molecules can experience
an instantaneous dipole
moment based on polarizability
Strength depends on MM

34. Types of Intermolecular forces
dipole-dipole forces:
polar molecules attract to each other when the positive end of one molecule is near the negative end of another
Depends on polarity

35. Types of Intermolecular forces
hydrogen bonding:
attraction between the H atom in a molecule with H-F, H-O, or H-N and an unshared electron pair on N,F, or O

36. Types of Intermolecular forces
hydrogen bonding:

37. Types of Intermolecular forces
Strength of IMF’s:
Dispersion < dipole-dipole < hydrogen bonding

38. Types of Intermolecular forces
Identify the IMF in each: Ar
H2O
HCl
CH3OH H2 HF
H2S

39. Properties of Water

40. Unique Properties of Water
1. Hydrogen bonds cause density of solid H2O to be less than liquid H2O, so ice floats. 2. Hydrogen bonds cause high surface tension in water.

41. https://www.youtube.com/watch? v=Hm52rkh68JA
Properties of Water
v=Hm52rkh68JA