Objectives Describe how a compound differs from an

Objectives • Describe how a compound differs from an element. • Identify parts of a chemical formula. • Explain why chemical bonding occurs. • CLE 3202. 1. 7 Construct chemical formulas for common compounds.

Chemical Bonds

Stability in Bonding A. Some elements combine chemically and no longer have the same properties they did before forming a compound

Stability in Bonding B. Compounds make up most of matter because arrangements of electrons in most atoms make them chemically unstable.

Stability in Bonding C. Stable atoms must have 8 electrons. Atoms share, gain or lose electrons to become more stable.

Stability in Bonding D. A chemical bond forms when an atom gains, loses or shares electrons.

Periodic Table

Stability in Bonding E. A chemical formula tells what elements make up a compound and the ratio of the atoms of those elements.

Stability in Bonding ØA chemical formula is composed of symbols and subscripts indicating the number of atoms of an element in a compound

Stability in Bonding Iron oxide (rust) Fe 2 O 3 2: 3 HC 2 H 3 O 2 1: 2: 3: 2 water H 2 O 2: 1 vinegar acetic acid sulfuric acid (battery acid) H 2 SO 4 2: 1: 4

Stability in Bonding F. An atom is chemically stable if its outer energy level is completely filled with electrons. Noble (inert gases) gases are chemically stable. He – 2 atoms H – 2 atoms Most others – 8

Stability in Bonding G. Atoms form compounds when the compound is more stable than the separate atoms.

Stability in Bonding 1. Noble gases are more chemically stable than other elements because they have a complete outer energy level.

Stability in Bonding 2. Elements that do not have full outer energy levels are more stable in compounds.

Stability in Bonding 3. Atoms can lose, gain, or share electrons to get a stable outer energy level.

Stability in Bonding 4. A chemical bond is the force that holds atoms together in a compound.

Why do elements form compounds? To become more chemically stable by getting a complete outer energy level

Objectives • Describe how a compound differs from an element. • Identify parts of a chemical formula. • Explain why chemical bonding occurs. • CLE 3202. 1. 7 Construct chemical formulas for common compounds.