• Six Types: 1) Dipole - Dipole, 2) Hydrogen-Bonding,

3) London Dispersion, 4) Metallic, 5) ionic, 6) Covalent (network solids)

Forces holding crystals togetherForces holding crystals together

Types of Crystalline Solids

Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl).

Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice).

Types of Crystalline Solids

Atomic Solid: Atoms at the points of the lattice that describe the structure of the solid (only one type of atom – diamond, graphite, copper).

Types of Crystalline Solids

Types of Crystalline Solids

Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice).

• Intermolecular forces (IMF) have to do with the attraction between molecules versus the attraction between atoms within a

molecule.

Intermolecular forcesIntermolecular forces

Molecular Solids

• WITHIN MOLECULES,

STRONG COVALENT BONDS

BETWEEN MOLECULES,

RELATIVELY WEAK FORCES (Intermolecular Forces)

• Two Types: 1) Dipole - Dipole Forces

Hydrogen-Bonding

2) London Dispersion (van der Waals) Forces,

Intermolecular forcesIntermolecular forces

Dipole - Dipole attractionsDipole - Dipole attractions•Polar molecules have a separation of charge

H Cl

+ –

• Molecules are attracted to each other in a compound by these + and – forces.

+ –

+ –

+ –

+ –

Hydrogen - bondingHydrogen - bonding

• H-bonding is a special type of dipole - dipole attraction that is very strong

• It occurs when N, O, or F are bonded to H

• They are given a special name (H-bonding) because compounds containing these bonds are important in biological systems

Water Molecules

London Dispersion forcesLondon Dispersion forces

• Non-polar molecules do not have permanent dipoles.

• London dispersion (or van der Waal) forces exist in non-polar molecules

are due to small dipoles that are temporary.

London Dispersion forcesLondon Dispersion forces

• Because electrons are moving around in atoms,

there will be instants when the charge around an atom is not symmetrical

• The resulting tiny dipoles cause attractions between atoms/molecules

London Dispersion forcesLondon Dispersion forces

relatively weak forces that exist among noble gas atoms and nonpolar molecules. (Ar, C8H18)

London forcesLondon forces

Instantaneous dipole: Induced dipole:

Eventually electrons are situated so that tiny dipoles form

A dipole forms in one atom or molecule, inducing a

dipole in the other

METALLIC SOLIDS

Atomic Solid: Metal Atoms at the points of the lattice.

Metallic BondingThe Electron Sea Model

Regular Array of Cations in a “Sea” of Valence Electrons

• Metals are good conductors because the valence electrons are able to flow freely

• Valence electrons of metals can be thought of as a “sea of electrons”

B. Types of Bonds

Metallic Bonding - “Electron Sea”

B. Types of Bonds

B. Types of Bonds

1

2

3

4

5

6

7

Metallic Bonding

Metals are found in:Groups 1 & 2

middle of table in 3-12

Below and to left of stairstep line

Have luster, are dutile and malleable

atom

METALLIC

Bond Formation

Smallest Unit

B. Types of Bonds

Types of Elements

e- are delocalized among metal atoms, “electron sea”

metals

IONIC SOLIDSContains ions at the points of the lattice (NaCl).

• HIGH MELTING SUBSTANCES

• HELD TOGETHER BY STRONG ELECTROSTATIC FORCES THAT EXIST BETWEEN OPPOSITELY CHARGES IONS

NaCl

II. Octet Rule

• In the formation of compounds, atoms tend to achieve the electron configuration of a noble gas.

• Atoms either gain, lose, or share electrons to form compounds.

III. CationsLoses an e-

-An atom’s loss of valence electrons produces a cation, or a positively charged ion.

III. Cations– Metals – lose valence e- easily– Transition metals – have 2 valence e-, usually lose

those two to form 2+ ions, but can also lose d electrons to form other ions

IV. Anions

– Nonmetals easily gain e- to form negative ions to get to 8 valence e-

Gains an e-

Chloride ion

IV. Anions-Nonmetals usually gain e-

Some can gain or lose, but will gain most often

Formula Unit-The lowest whole-number ratio of ions in an ionic compound.

V. Ionic Bonds

• When oppositely charged ions attract, electrostatic force that holds them together = ionic bond

• Compounds containing ionic bonds = ionic compounds

• Electrons are transferred from cations to anions

• Bonds formed between metals and nonmetals (or contain a polyatomic ion)

V. Ionic Bonds

Na·

1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p5

RESULTS IN

Na+

1s2 2s2 2p6 1s2 2s2 2p6 3s2 3p6

VI. Properties of Ionic Compounds

• Most ionic compounds are crystalline solids at room temperature.– Arranged in repeating three-dimensional

patterns

• Ionic compounds generally have high melting points– Large attractive forces result in very stable

structures

VI. Properties of Ionic Compounds

• Ionic compounds can conduct an electric current when melted or dissolved in water.– When ionic compounds are dissolved in water

the crystalline structure breaks down. This allows the ions to move freely which results in conductivity.

• The positive Na ions move to the cathode and the negative Cl ions move to the anode.

NETWORK ATOMIC SOLIDS: (CARBON & SILICON)

SOLIDS CONTAINING STRONG DIRECTIONAL COVALENT BONDS TO FORM A SOLID THAT MIGHT BE BEST VIEWED AS A “GIANT MOLECULE”

EXAMPLE:

DIAMOND AND GRAPHITE

The Structures of Diamond and Graphite

The Structure of Quartz

Si at the center

of tetrahedral arrangement with 4 oxygen atoms.