Stability in Bonding Section 19.1

Stability in Bonding Statue of Liberty is green- Statue of Liberty is green- made out of copper made out of copper Copper reacts with sulfur and oxygen Copper reacts with sulfur and oxygen Reactants: Copper, oxygen, sulfur, carbon dioxide, water Reactants: Copper, oxygen, sulfur, carbon dioxide, water Products: Cu 4 SO 4 (OH) 6, Cu 2 CO 3 (OH) 3, Cu 3 (CO 3 ) 2 (OH) 2 Products: Cu 4 SO 4 (OH) 6, Cu 2 CO 3 (OH) 3, Cu 3 (CO 3 ) 2 (OH) 2 Properties of the elements are very different than properties of the compounds in a chemical reaction Properties of the elements are very different than properties of the compounds in a chemical reaction Hydrogen + oxygen  Water Hydrogen + oxygen  Water Colorless gases  Colorless liquid Colorless gases  Colorless liquid Flammable Supports combustion  Puts out fires

Chemical Formulas Chemical Formula- tells how many of each element are present in a compound Chemical Formula- tells how many of each element are present in a compound Consists of element symbols and subscripts Consists of element symbols and subscripts Water has 2 hydrogen atoms and 1 oxygen atom Water has 2 hydrogen atoms and 1 oxygen atom

What do the formulas mean? SiO 2 SiO 2 silicon- 1 Oxygen-2 silicon- 1 Oxygen-2 C 12 H 22 O 11 C 12 H 22 O 11 Carbon- 12 Hydrogen-22 Oxygen-11 Carbon- 12 Hydrogen-22 Oxygen-11 N 2 O N 2 O Nitrogen- 2 Oxygen-1 Nitrogen- 2 Oxygen-1

Why do compounds form? Atoms combine because the compound is more stable than the individual elements Atoms combine because the compound is more stable than the individual elements They have the wrong number of electrons to be stable alone and must share or exchange electrons They have the wrong number of electrons to be stable alone and must share or exchange electrons Noble gases don’t form compounds because they are stable Noble gases don’t form compounds because they are stable Chemically stable- have 8 valence electrons Chemically stable- have 8 valence electrons Valence electrons- outer energy level electrons- the electrons that determine chemical properties Valence electrons- outer energy level electrons- the electrons that determine chemical properties

Valence electrons # at the top is valence Except for He, which has only 2

Stability Hydrogen, helium, lithium, beryllium, and boron need 2 valence electrons in their outer energy level to be stable Hydrogen, helium, lithium, beryllium, and boron need 2 valence electrons in their outer energy level to be stable Others need 8 to be stable – usually. Others need 8 to be stable – usually. Electron dot diagrams- include the element symbol and dots to represent valence electrons Electron dot diagrams- include the element symbol and dots to represent valence electrons Can use electron dot diagrams to help us determine stability- Can use electron dot diagrams to help us determine stability- H is less stable than He because it has only 1 valence electron while He has 2 valence electrons H is less stable than He because it has only 1 valence electron while He has 2 valence electrons

How do atoms become stable? They share, gain, or lose electrons to become stable They share, gain, or lose electrons to become stable Chemical bond- force that holds atoms together in a compound – caused by either exchanging or sharing electrons Chemical bond- force that holds atoms together in a compound – caused by either exchanging or sharing electrons