PAP Chapter 6 PAP Chapter 6 CHEMICAL CHEMICAL BONDINGBONDING

PAP Chapter 6 PAP Chapter 6 CHEMICAL CHEMICAL BONDINGBONDING

Cocaine

Chemical BondingChemical BondingA chemical bond is a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together

Metallic Bonding

Metallic – holds atoms of metals togetherA metallic bond is formed between all

metals. Examples include a piece of Copper, Zinc, Sodium, Iron. Any metal

Metallic bonds result from the attraction between metal atoms and the surrounding sea of delocalized electrons

valence electrons can move freely around the whole metal structure—they are not confined to any one atom

Characteristics of Metals

ODuctile- draw into thin wireOMalleable-ability to hammer into

O Thin sheetsOShiny (luster)OConducts heat and electricity OSolid at room temperature

Metallic BondingThis model explains many of the

properties of metals: the mobile electrons can enter/leave

the metal structure, so metals are good conductors of heat and electricity!

metal cations are not locked into any crystal structure, so they can slide past each other when stressed. That makes metal malleable and ductile.

The de-excitation ( The electron falling back down to a lower energy level) is responsible for the shiny (luster) appearance of metals.

Ionic BondsOcomplete transfer

of 1 or more electrons from one atom to another (one loses, the other gains) forming oppositely charged ions that attract one another

Remember Cations and Anions

An atom which loses an electron becomes positively charged and is called a cation.

Examples: Na+, K+, Ca2+, Al3+

Metals usually become cations

An atom which gains an electron becomes negatively charged and is called an anion.

Nonmetals usually become anions.

Examples: Cl-, S2-, N3-

Characteristics of Ionic Bonds

The electrons align themselves into an orderly arrangement that is known as crystal lattice. This makes the shape that you see into a crystal.

Characteristics of Ionic Compounds

Strong attraction between ionsSoluble in waterConduct electricity in solutionConduct electricity when

moltenHigh melting pointsHigh boiling pointsHard but brittleSolid at room temperature

What are electron dot formulas orLewis Dot Diagrams

Electron dot formulas are diagrams that show valence electrons in the atoms of an element as dots around the symbol of the element.

1.1. Make Generalizations Make Generalizations As illustrated by the electron dot formulas in the table, how are the elements in a group similar?

1.1. Make Generalizations Make Generalizations As illustrated by the electron dot formulas in the table, how are the elements in a group similar?

How are electron dot formulas for ionic bonds constructed?

Ionic bonds form as a result of electrostatic attractions between cations and anions.

Electron dot formulas show the valence electrons and charges of these ions and may be used to illustrate the ionic bonds.

Examples

ExamplesO Lithium and BromineO Magnesium and ChlorineO Sodium and SulfurO Aluminum and Oxygen

Day 2

Covalent BondsCovalent Bonds:Covalent —valence electrons are shared between nonmetal atoms

Covalent BondNonpolar Covalent bond- Covalent

bond in which the bonding electrons are shared equally by the bounded atoms, resulting in a balanced distribution of an electrical charge.

Polar Covalent bond- Covalent bond in which the bonded atoms have an unequal attraction for shared electrons. Each atom has a chargePartial positive- (+δ) Partial negative- (- δ)

Characteristics of Covalent Bonds

OTwo non-metals bonded together

ORelatively weak bondsOUsually a gas or liquid at room

temperatureODoes not conduct electricity in

solutionOLow melting pointOLow boiling pointOSoluble in alcohol and insoluble

in water

The type of bond can usually be calculated by finding the difference in electronegativity of the

two atoms that are going together.

ElectronegativityIncreases

ElectronegativityDecreases

OIf the difference in electronegativities is between:O 1.8 to 4.0: IonicO 0.4 to 1.7: Polar CovalentO 0.0 to 0.3: Non-Polar Covalent

Example: NaClNa = 0.9, Cl = 3.0Difference is 2.1, sothis is an ionic bond!

Electronegativity Difference

Example: H2OH = 2.1, O = 3.5Difference is 1.4, sothis is a polar covalent bond !

ODiatomic Molecules are nonpolar covalent compounds.

OA diatomic molecule is a molecule only containing two atoms

OThe seven diatomic molecules areOH2, N2, O2, F2, Cl2, Br2, I2OThese diatomic molecules are never by themselves.

Diatomic Molecules

Octet RuleOctet Rule

Chemical Compounds tend to form so that each atom, by gaining, losing or sharing electrons, has an octet of eight electrons in its highest occupied energy level

Electron dot formulas:covalent bonds O In a covalent bond, no ions form. Instead, nonmetallic

atoms share electrons, which results in each atom having a noble-gas configuration.

O Single Covalent Bonds -A single covalent bond results when two atoms share one pair of electrons, as in the case of hydrogen gas, which is a diatomic molecule.

OExamples: F2 , HBr, Cl4

(contd.)

ODouble Covalent Bonds- When atoms bond by sharing two pairs of electrons, the result is a double covalent bond, as in a molecule of carbon dioxide, CO2. The double bond is shown by four dots or two dashes.

Triple Covalent Bonds- When atoms bond by sharing three pairs of electrons, the result is a triple covalent bond, as in a molecule of nitrogen gas, N2. The triple bond is shown by six dots or three dashes.

Violations of the Octet RuleViolations of the Octet RuleUsually occurs with B and elements of Usually occurs with B and elements of

higher periods. Common exceptions are: higher periods. Common exceptions are:

Be, B, P, S, and Xe. Be, B, P, S, and Xe.

BF3BF3

SF4SF4

Be: 4

B: 6

P: 8 OR 10

S: 8, 10, OR 12

Xe: 8, 10, OR 12

Lewis Structures

HF

H2O

H F

or H - F

H O H

or H - O - H

NH3

CH4

H N HH

or H - N - H

H

H C HH

H

or H - C - H

H

H

Lewis Structures

Extra Slides

H2O is POLAR because it has a positive end and a negative end. (difference in electronegativity)

O has a greater share in bonding electrons than does H.

O has a greater share in bonding electrons than does H.

O has slight negative charge (-δ) and H has slight positive charge (+ δ)

Bond Polarity

This is why oil and water will not mix! Oil is nonpolar, and water is polar.

The two will repel each other, and so you can not dissolve one in the other

Bond PolarityBond Polarity

Bond PolarityBond Polarity

“Like Dissolves Like”Polar dissolves PolarNonpolar dissolves

NonpolarPolar also dissolved

IonicEx: water and salt