1. Chemical Bonding and Chemical Reactions
Chapter 16 and 17
Chemical Bonding and Chemical Reactions

2. Chemical Bonding The force that holds two atoms together
Unites atoms in a molecule
Atoms bond so they will become more stable. Their outer rings will resemble the noble gases.

3. Ionic Bonds Ion Ionic Bond Atom that has lost or gained an electron
Is now positive or negatively charged
Ionic Bond
Attraction that holds oppositely charged ions close together
Positive Na ion and negative Cl ion are attracted to one another.

4. Ionic Bond

5. Covalent Bonds
Chemical bond that forms between nonmetal when they share electrons
Electrons move back and forth between the outer energy levels of each atom to maintain the covalent bond

6. Molecule The neutral particle formed when atoms combine 2 Types:
Element or Compound
Element—Molecule formed from 1 type of atom
Compound—Molecule formed from 2 or more types of atoms

7. Symbols for Compounds
Compounds can be described using element symbols and numbers
Subscripts (small numbers) after the letters tell how many of that element are in a molecule.
Example: H2O contains 2 Hydrogen atoms and 1 oxygen atom.

8. Chemical Formula
Combination of chemical symbols and numbers that shows which elements are present in a compound and how many atoms of each element are present.
Examples:
Ammonia: NH3
Silver Tarnish: Ag2S
Hydrogen Gas: H2

9. Chapter 17
Chemical Reactions

10. Physical or Chemical Change?
Physical Change
Affects the physical appearance of a substance
Changes in state
Changes in shape or size
Chemical Change
Produces a new substance during a chemical reaction
Produces gas, light, change in heat, precipitate, change in color, sound
Oxidation, Burning

11. Physical or Chemical Change?

12. Chemical Equations
Describes the reactants and products in a chemical reaction using symbols and numbers
Reactants
Substances that exist before the reaction begins
Products
Substances that form as a result of the reaction

13. Writing Chemical Equations
Reactants Products
2H2 + O H20
Hydrogen + Oxygen Water
2 Ag + H2S Ag2S + H2
Silver + Hydrogen Sulfide Silver Sulfide + Hydrogen

14. Conservation of Mass Matter is not created or destroyed
Every atom that appears on the reactant side of the reaction also appears on the product side of the reaction

15. Balancing Equations
Ag + H2S Ag2S + H2
H2 + O2 H20

16. pH Scale Scale used to measure the strength of an acid or base.
is considered an acid (battery acid)
Releases H+ ions in a solution
7 is considered neutral (water)
7.5—14 is considered a base (lye, soap)
Releases OH– ions in a solution

17. pH Scale

18. Energy in Chemical Reactions
Endothermic Reaction
Reaction that absorbs heat energy (gets colder)
2H20 + energy H2 + O2
Exothermic Reaction
Reaction that releases heat energy (gets warmer)
CH4 + 2O CO2 + H2O + energy

19. Activation Energy
Minimum amount of energy need to start a chemical reaction
Example—burning of gasoline

20. Catalyst A substance that speeds up a chemical reaction
Are not changed permanently or used up during a chemical reaction
Enzymes
Special Catalysts that speed up chemical reactions in cells.

21. Inhibitor Substance that slows down a chemical reaction
Makes the formation of a certain amount of product take longer