Structure & Bonding - overview

I. Intramolecular forces: (& electronegativity) - Metallic bonding & alloys - Ionic bonding & formula units/salts

- Bond formation - Properties - Names & formulas

- Covalent bonding & molecules - Bond formation (including; types, strength, length, & Energy) - Properties - Names & formulas

II. Lewis Dot Diagrams & Structures - Octet Rule - Bonding & Non-bonding electron pairs - Exceptions to octet - Resonance

III. VSEPR theory - Molecular Geometry Names & Shapes - Bonding angles - Polarity (molecules & bonds) - Hybridization

Chemical Bonds are forces of attraction between elements.

- Bonds that form compounds are called intra-molecular forces.

- Bonds that form between 2 different compounds are called inter-molecular forces.

Example of chemical bonding

1. Intra-molecular Bonds (occur inside a compound) Are the Chemical Bonds or Forces that hold elements together, forming compounds.

- There are 3 main types of intramolecular bonding forces, in decreasing strength.

1. Ionic bonds, form ionic compounds (formula unit).

2. Metallic bonds, form metallic compounds (alloy).

3. Covalent bonds, form covalent compounds (molecule).

______________________________________________

Metallic Bonds hold Alloys together.

- 2 or more metal elements bonded together, are called an Alloy or metallic compound.

- Alloys are held together by delocalized electrons, that are able to move throughout (3-D) the

metal atoms, and not attracted to any specific atom, called the electron sea model.

(Delocalized electrons are the cause for magnetism)

Intramolecular Bond Types:

1. Ionic bond (compounds) If the Electronegativity difference is equal to or greater than 1.7

2. Covalent Bonds (compounds)

a. Polar Covalent bonds If the Electronegativity difference is between 1.7 0.5 (& equal to 0.5)

b. Nonpolar Covalent bonds If the Electronegativity difference is less than 0.5

_______________________________________________________

- Ionic Bonds (form ionic compounds, called Formula Unit or Salt)

- Is a strong attractive force between Cation (metal) + Anion (non-metal).

- One element gains an electron and one element loses an electron called transfer. (ionic bonds are stronger than covalent & metallic bonds.)

Example:

Ionic Compound Properties: Are Hard & Brittle with high melting and boiling points.

Ionic solids form crystal lattice structures.

Are Soluble(dissolves) in water, but insoluble( doesn't dissolve) in organic solvents (like oil or alcohol).

Conduct electricity when molten or aqueous, called an electrolyte

A Crystal Lattice is a tightly packed geometric arrangement of formula units.

- Lattice Energy is needed to break the force of attraction between the (+) and (-) ions arranged in a crystal lattice.

- This lattice energy is why ionic compounds are so strong (high melting & boiling pts.)

- Electrolyte is any compound that conducts electricity when melted or dissolved in water (aqueous).

- An ionic compound is an electrolyte because it conducts an electric current when it is dissolved in water, producing ions

(+) and ( - ).

Sodium chloride in solution

NaCl

Covalent Compounds

Also called Molecular compounds

also called molecules

Properties include: Are usually soft, and easily deformed. (like silly putty)

Mainly Gases or Liquids at room temperature.

Molecules have low melting points, low boiling points.

Tend to be insoluble in water, but will dissolve in organic solvents. Do not conduct electricity in water (poor electrolytes).

Allotropes are forms of an element in the same state (Solid, Liquid),

that have different structures(arrangements) & properties.

Coal Graphite

Diamond, are all carbon compounds.

A molecular compound is a molecule, held together by a covalent bond.

A molecule forms when 2 atoms Share a pair of electrons.

1. Single bond = weakest strength + longest length. - Are one bond formed from sharing 2 electrons.

2. Double bond = medium strength + medium length. - Are two bonds formed from sharing 4 electrons.

3. Triple bond = strongest strength + shortest length.

- Are three bonds formed from sharing 6 electrons.

Example

Example

Example

_______________________________________________________

_______________________________________________________

Energy is absorbed when bonds break, and energy is released when bonds form.

The amount of energy required to break a covalent bond is called the bond Dissociation Energy (always (+) value).

(exothermic) (endothermic)

The longer the bond length, the weaker it is and less energy is needed to break it.

The shorter the bond length, the stronger it is and more energy is needed to break it.

Sigma bonds are Single bonds (ALWAYS the 1st bond formed) - involve the S orbitals.

Pi bonds are double or triple bonds (the 2nd & 3rd bonds to form between same two atoms). - involve P orbitals, overlapping above and below sigma bonds.

Covalent Bond Types can be polar or non-polar - Non-polar bonds have an electronegativity difference equal or less than 0.4 - Polar bonds have an electronegativity difference greater than 0.4 and less than 1.7

Molecular Polarity is determined by 1. Asymmetrical, meaning the central atom has additional non-bonding electrons. (Binary molecules = uneven electron distribution)

2. has Polar Bonds between the atoms.

____________________________________________________________

-The more electrically negative element is labeled ..

-The more electrically positive element is labeled .. Example:

Example

(is the entire molecule polar or nonpolar)

Labeling Polar Bonds