ch. 8 – covalent compounds i. bond polarity and imf (237 – 241)
TRANSCRIPT
Ch. 8 – Covalent CompoundsCh. 8 – Covalent CompoundsCh. 8 – Covalent CompoundsCh. 8 – Covalent Compounds
I. Bond Polarity and IMF
(237 – 241)
A. Bond PolarityA. Bond Polarity
Most bonds are a blend of ionic and covalent characteristics
Difference in electronegativity determines bond type
A. Bond PolarityA. Bond Polarity
Electronegativity
• Attraction an atom has for a shared pair of electrons
• higher e-neg atom -
• lower e-neg atom +
• Draw the Lewis structure for HCl & label partial charges
A. Bond PolarityA. Bond Polarity
Determine bond polarity:• C – O• Ca – O• Si – Cl• H – F• N – N
• 3.44 – 2.55 = 0.89
• 3.44 – 1.00 = 2.44
• 3.16 – 1.90 = 1.26
• 3.98 – 2.20 = 1.78
• 3.04 – 3.04 = 0.00
• PC
• Ionic
• PC
• Ionic
• NPC
B. Molecular PolarityB. Molecular Polarity
Polar molecule = one end slightly + and one end slightly –
Molecule with 2 poles = dipolar molecule or dipole
B. Molecular PolarityB. Molecular Polarity
Shape, symmetry and bond polarity determines molecular polarity
H – O bond is polar and water is asymmetrical, so H2O is polar
C – Cl bond is polar, but CCl4 is symmetrical, so molecule is nonpolar
B. Molecular PolarityB. Molecular Polarity
Identify each molecule as polar or nonpolar
• SCl2
• O2
• CS2
• CF4
• CH2F2
Tetrahedral, bent → polar
Nonpolar bonds → nonpolar
Linear → nonpolar
Tetrahedral → nonpolar
Tetrahedral → polar
C. Definition of IMFC. Definition of IMF
IMF = Intermolecular ForcesAttractive forces between molecules
Much weaker than chemical bonds within molecules
D. Types of IMFD. Types of IMFVan der Waals
D. Types of IMFD. Types of IMF
London Dispersion Forces
View animation online.
D. Types of IMFD. Types of IMF
Dipole-Dipole Forces
+ -
View animation online.
D. Types of IMFD. Types of IMF
Hydrogen Bonding
PCl3• polar = dispersion, dipole-dipole
CH4
• nonpolar = dispersionHF
• H-F bond = dispersion, dipole-dipole, hydrogen bonding
E. Determining IMFE. Determining IMF
Substances in which all atoms are covalently bonded to each other• Very stable
Examples • Diamonds – Carbon covalently
bonded to carbon• Quartz – SiO2 covalently bonded
and not distinct molecules
F. Network SolidsF. Network Solids
II. Ions(p. 194 – 200)
Ch. 7 – Ionic Bonds & Ch. 7 – Ionic Bonds & PropertiesProperties
Ch. 7 – Ionic Bonds & Ch. 7 – Ionic Bonds & PropertiesProperties
The lowest whole-number ratio of ions in an ionic compound
A. Formula Unit
• Oppositely charged ions attract, force that holds them together = ionic bond
• Electrons are transferred from cations to anions
• Bonds formed between metals and nonmetals (or contain a polyatomic ion)
B. Ionic Bonds
• Most ionic compounds are crystalline solids at room temp
• Ionic compounds generally have high melting points
• Large attractive forces result in very stable structures
B. Properties of Ionic Compounds
III. Bonding in Metals(p. 201 – 203)
Ch. 7 – Ionic and Metallic BondingCh. 7 – Ionic and Metallic BondingCh. 7 – Ionic and Metallic BondingCh. 7 – Ionic and Metallic Bonding
A. Metallic CharacterA. Metallic Character
1
2
3
4
5
6
7
Metals Nonmetals Metalloids
• good conductors because the valence electrons are able to flow freely
• Valence electrons of metals can be thought of as
a sea of electrons
• Properties can be explained by the mobility of electrons in metals
B. Metals
“electron sea”
METALLICBond Formation
Smallest Unit
MeltingPoint
E. SummaryE. Summary
Physical State @ RT
e- are delocalized among metal atoms
very high
solid