Chemical Bonding…. How Atoms Combine Bonding involve electrons in the outermost energy level Valence Electrons.

Chemical Bonding…. How Atoms Combine

Bonding involve electrons in the outermost energy level

Valence Electrons

All Elements want to be stable….Their valence level is filled with 8 electrons. This is called the Octet Rule.

THREE DIFFERENT TYPES OF BONDS

1. Ionic bonds –-Between Metals and Nonmetals

2. Covalent bonds -Between Nonmetals3. Metallic bonds- Between Metals

To do this… atoms will bond by

Electron Transfer (Ionic):

1. Giving out electrons (Losing electrons)2. Taking electrons (Gaining

electrons) OR

3. Sharing Electrons (Covalent)

When electrons are gained, lost, or shared, an attractive force is formed. This is called a BOND and holds the elements in a compound together.

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Ionic Bonding

• This type of bonding occurs when electrons are moved from one atom to another.

• The charged particle that forms is called and ION.

When an atom loses (or gives away) its electrons, it becomes positively charged. This is known as a CATION.

The Alkali Metals commonly form Positive Ions.

When an atom gains electrons, it becomes negatively charged. This is known as an ANION.

The Halogen Family commonly forms Negative Ions.

Positive Ions attract Negative Ions to form

Ionic Bonds

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Ionic Bond

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When Ions bond, they form a repeating, 3-dimensional pattern called a Crystal Lattice.

The strong attraction between ions in a crystal lattice gives ionic compounds certain properties such as:

Brittleness

Because ionic bonds are so strong, their melting points are very high. Ionic compounds are usually solids at room temperature.

High Melting Points

·Soluble

·Good Conductors*

Combining Power

The number of electrons that an element can lose, gain, or share is called its Oxidation Number.

All the positive ions have to equal the negative ions. For example:

NaCl or AlCl3

In a compound, the sum of the oxidation numbers is ZERO.

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· Some elements have more than one oxidation number. For example: Iron = 2+ or 3+. …. Fe(II) or Fe(III). Roman numeral following the symbol tells the oxidation number!

Element Valence Oxida-tion #

Element Valence Oxida-tion #

Formula

Aluminum Chlorine

Magnesium Bromine

Sodium Oxygen

Lithium Oxygen

Calcium Phosphorous

Carbon Chlorine

Aluminum Oxygen

Beryllium Sulfur

Sodium Fluorine

Silicon Neon

Writing Formulas for Ionic Compounds

1. Write the symbols (write the positive ion first).2. Write the oxidation number over the top of each symbol.. Reduce if possible.3. Criss-Cross the oxidation numbers and make them subscripts.

Naming Ionic Compounds

(Metal & Nonmetal)

*Name the 1st element then Name the 2nd element with "IDE" ending.

For example: NaCl = Sodium Chloride BaF2 = Barium Fluoride Al2O3 = Aluminum Oxide

Electron Sharing: Covalent Bonds

· Electrons are sometimes SHARED between the atoms. The valence levels join together. The bond is called ___________________.

· The smallest unit of a covalently bonded compound is called a ____________.For example: The bond between Hydrogen and Chlorine.

(See Page ____________)

H

Cl

Atoms can sharemore than onepair of electrons

Some ELEMENTS exist in nature as covalent bonds. They are called_

Diatomic Molecules

The ‘Heavenly 7’

Naming Covalent Bonds

· A prefix is used before the name of an element to indicate the number of atoms in that compound....CO2 = Carbon

Dioxide

CO = Carbon Monoxide

· 'Mono" is only used before the second element in a compound. It is never used for the first. (All other prefixes are used for the first element.

For example: CO = Carbon Monoxide C2O2 = Dicarbon Dioxide

Know those prefixes!!!

1 = mono2 = di3= tri4 = tetra5 = penta6 = hexa7 = hepta8 = octa9 = nona10 = deca

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