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 Nonmetals 3.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. *

Ionic Bonding This type of bonding occurs when electrons are moved from one atom to another. The charged particle that forms is called an 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 *

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 AlCl 3 In a compound, the sum of the oxidation numbers is ZERO. *

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.