IIIIIIIV Chemical Bonding Covalent / Molecular Compounds.

I II III IV

Chemical Bonding

Covalent / Molecular Compounds

Properties of Covalent Bonds

Bond Formation Electrons shared between two nonmetals

Type of Structure True Molecules

Physical State Liquid or Gas

Melting Point Low

Solubility in Water Usually not

Electrical Conductivity No

Other Properties Odorous

Nonpolar Covalent Bond e- are shared equally symmetrical e- density usually identical atoms

Bond Polarity

N O F

Cl

Br

I

H

Nonpolar Covalent Molecules

The Seven Diatomic Elements

Br2 I2 N2 Cl2 H2 O2 F2

+ -

Bond Polarity

Polar Covalent Bond e- are shared unequally asymmetrical e- density results in partial charges (dipole)

Bond Polarity

Remember, most bonds are a blend of ionic and covalent characteristics.

Difference in electronegativity determines bond type.

Bond Polarity

Examples:

Cl2

HCl

NaCl

3.0-3.0=0.0Nonpolar

3.0-2.1=0.9Polar

3.0-0.9=2.1Ionic

+ -

+

Lewis Structures

Nonpolar Covalent - no charges

Polar Covalent - partial charges

Naming Covalent Compounds

Prefix System (binary compounds)

1. Less e-neg atom comes first.

2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.

3. Change the ending of the second element to -ide.

PREFIXmono-di-tri-tetra-penta-hexa-hepta-octa-nona-deca-

NUMBER12345678910

Molecular Nomenclature

CCl4

N2O

SF6

carbon tetrachloride

dinitrogen monoxide

sulfur hexafluoride

Molecular Nomenclature

arsenic trichloride

dinitrogen pentoxide

tetraphosphorus decoxide

AsCl3

N2O5

P4O10

Molecular Nomenclature

Metallic

Bonding

“electron sea”

METALLICBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

MeltingPoint

Properties of Metallic Bonds

Physical State

e- are delocalized among metal atoms

very high

yes (any form)

no

malleable, ductile, lustrous

solid

Metallic Bonds

Metal atoms are held together in the solid through metallic bonding.

Metals hold on to their valence electrons very weakly.

Think of them as positive ions (cations) floating in a sea of electrons.

Sea of Electrons

+ + + ++ + + +

+ + + +

Electrons are free to move through the solid.

This is why metals are able to conduct electricity.

Metals are…

Metals are malleable - hammered into shape (bend).

Also ductile - drawn into wires.Both malleability and ductility

demonstrate the mobility of the valence electrons

Intermolecular Forces

Intramolecular vs Intermolecular

Intramolecular - forces that hold particles together in ionic, covalent and metallic bonds

Intermolecular - attractions between one molecule and a neighboring molecule.

Intermolecular Forces

Types of intermolecular forces: Dispersion forces Dipole-dipole Hydrogen bonds

Dispersion forces

Weak forces that result from temporary shifts in the density of electrons in electron clouds, creating an induced dipole.

Weakest of the intermolecular forcesExists between identical atoms

Dipole-dipole forces

Attractions between oppositely charged regions of polar molecules

Stronger than dispersion forcesExists between polar covalent molecules

Hydrogen bonding

Special type of dipole-dipole attraction that occurs between molecules containing a hydrogen atom bonded to a small, highly electronegative atom with at least one lone electron pair.

Occurs between hydrogen and either fluorine, oxygen, and nitrogen atoms only.

Strongest of the forces

Hydrogen bonding

Properties of Hydrogen Bonding

Stronger forces=higher melting/boiling points

Weaker forces=lower melting/boiling points