Ch. 8 – Covalent Compounds I. Bond Polarity and IMF (237 – 241)

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