1. The rules to

4. The TWO basic rules  Opposites ATTRACT and likes REPEL  Nature moves in the direction of the least resistance (lowest energy)

5. Valence Shell Valence electrons  The valence shell is the outer most shell  Valence electrons have the highest energy level. –usually “s” and “p”

7. The OCTET RULE  chemical rule of thumb that reflects observation that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

8. Octet Rule

9. Electronegativity  The measure of the atom’s ability to attract electrons to itself  Noble gases have an electronegativity of ZERO due to the valence shell containing 8 e-

10. Electronegativity

11. Noble Gases have 8 e- in valence shell

12. Chemical Bonding  The process in which elements combine to form a compound

13. Chemical Bonding….

14. Chemical Bond  The electrostatic attractive forces between atoms STRONG enough for the atoms to act as a single unit  Created by the transferring or sharing of electrons

15. TWO major types  IONIC and COVALENT

16. COVALENT BOND  A covalent bond is formed when atoms share electrons.  single covalent bond — one electron is shared  double covalent bond — two electrons are shared  triple covalent bond — three electrons are shared

17. Covalent Bonds

18. Polar Water Molecule  The shared electrons in a covalently bonded molecule may spend more time near one atom than the other.  The shared electrons in a water molecule spend more time near the oxygen than the hydrogen atoms.  This distribution of electrons gives the molecule a slight positive charge on the hydrogen side of the molecule and a slight negative charge on the oxygen side of the molecule.

19. Non-Polar = evenly sharing Polar = one using the e- more than the other (not even)

20. IONS  Ions are formed from the loss and gain of e-  Cation – electrical charge is +  Anion – electrical charge is -

21. Ionic Bonds

22. IONIC BONDS  An ionic bond is formed when electrons are transferred from one atom to another.  Ionic bonds are most often formed between atoms that have fewer than two electrons in their outer electron shell and those that have almost full outer electron shells.

23. Hydrogen Bond  A bond between hydrogen atoms already covalently bonded in a molecule to oppositely charged particles  Hydrogen bonds are weaker than ionic or covalent bonds.  They are formed mostly between molecules.  They can also form between parts of the same molecule.

24. Chemical Reactions  The formation and breaking of chemical bonds  They require energy input or release energy.  Three types of chemical reactions: 1. Synthesis 2. Decomposition 3. Exchange reactions

26. Chemical Reactions  Factors that influence reaction rates  Concentration of reactants  Temperature of the environment  Activation energy  Some reactions require the presence of a catalyst or enzyme.  Reaction speed is increased when there are more catalyst proteins present.