2.3 Comparing the Properties of Ionic
and Molecular Compounds
Learning Goals …
… compare properties of ionic and covalent
compounds
… determine the shape of a molecule
MELTING AND BOILING POINTS
• the strength of the force between ions or molecules
determines the melting point and boiling point of a
compound
• ionic compounds usually have HIGH melting points and
boiling points
• polar covalent compounds have intermediate m.p.’s and
b.p.’s
• non-polar molecules have the lowest m.p. and b.p
SOLUBILITY
•
•
•
•
water is a POLAR molecule
“like disolves like”
ionic and polar covalent compounds are soluble in water
non-polar compounds are insoluble in water
ELECTRICAL CONDUCTIVITY
• ions must be free to move in order to conduct an electric
current
• only IONIC compounds in the liquid or aqueous state can
conduct electricity
Molecular Shapes
Linear
Tetrahedral
Trigonal planar
Bent
Trigonal
pyramidal
Bent
Predicting Molecular Shape
a) BeF2
2 bond pairs
0 lone pairs
LINEAR
b) BCl3
3 bond pairs
0 lone pairs
TRIGONAL PLANAR
c) SiCl2
Si
2 bond pairs
1 lone pairs
BENT
d) CF4
4 bond pairs
0 lone pairs
TETRAHEDRAL
e) PF3
3 bond pairs
1 lone pairs
TRIGONAL
PYRAMIDAL
f) H2O
2 bond pairs
2 lone pairs
BENT
Can I …
… compare properties of ionic and covalent
compounds
… determine the shape of a molecule
HOMEWORK
WS “Properties of Ionic and Molecular Compounds”
p 82 #4-6, 8, 11-13, 16