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chemistry continued

CHEMICAL REACTIONS

IV). Electron Shells

The first shell can hold 2 electrons all other shells can hold 8 electrons.

Each energy level wants to be filled by either gaining, losing, or sharing electrons in the outer shell.

The outer most shell is called the valence shell.  This is the only chemically active shell

How to determine electron shells:

 

 

V). Chemical Bonds

    A). Ionic Bonds

An electron transfer between atoms

                            The positively charged ion is the cation,

                             and the negatively charged ion is the anion.

Ionic bonds only occur when the atom needs to gain or lose 1 or 2 electrons

    B). Covalent Bonds

Charged ions share electrons

In nonpolar molecules shared equally.

In polar molecules  not shared equally

Covalent bonds occur when an atom needs to gain or loss more than 2 electrons

    C). Hydrogen Bonds

Hydrogen bonds form when hydrogen already covalently bonds

 

VI). Chemical Reactions

        A). chemical equations

Chemical equations must be balanced

        B). Types of reactions

1). Synthesis Reaction: A + B >AB

            (anabolic)

2). Decomposition Reaction: AB  > A + B

                                 ( catabolic)

 

3). Exchange or Displacement Reactions

                                    AB + C >AC + B or AB + CD > AD 

4). Oxidation-Reduction Reactions

                                    The electron donor is oxidized.

                                   The electron acceptor is reduced.

 

5). Hydrolysis Reaction

B). Energy Flow

Chemical reactions result in the net absorption or release of energy

1). Exergonic Reaction

 

2). Endergonic Reacton

 

C). Factors influencing chemical reactions

                                CATALYSTS

Catalysts lower the amount of energy need for the reaction to occur thus speeding up the reaction without being used up themselves.

atom animation from hotbar.com