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Cont. Physcial Science

Test Date: 11/15/04

Bonding and Reactions

Study Guide

There are three types of bonding.

  1. Ionic Bonding- bonding between a metal and a non-metal. This bonding always involves a transfer of electrons.

Important Information:

  • Valence Electrons: The number of electrons found in the outer most shell of an atom.
  • An atom that gains an electron has a negative charge. It is called a negative ion.
  • An atom that loses an electron has a positive charge. It is called a positive ion.
  • In ionic bonding electrons are taken from one atom by another.
  • In Ionic Bonding, atoms will gain or lose electrons in a chemical reaction in order to have 8 valence electrons. You must have 8 valence electrons in order to have a stable electron configuration (“Octet Rule”)
  • Electron Dot Diagram (Page 159): In this diagram each dot represents a valence electron. In most cases the group that an element is found in is equal to the number of valence electrons of an atom. Ex. Since potassium (K) is in group 1 it has one valence electron.
  • Ionic bonds are considered to be strong bonds.

Example of how to draw an Ionic Bond (Page 159 in Text)

The following is the drawing of an ionic bond between Magnesium (Mg) and Oxygen (O)

Step 1: Draw Magnesium and Oxygen (showing only the outer most shell)

Step #2: Decide which atom will lose an electrons and which atom will gain electrons.

Step #3: Draw the new bonded atom.

Practice Problem:

Show an Ionic bond between Cesium (Cs) and Chlorine (Cl)

  1. Covalent Bonding- a chemical bond in which two atoms share a pair of valence electrons. This occurs between a non-metal and a non-metal.
  • The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond.

Example of how to draw a Covalent Bond:

Draw the covalent bond of

Step #1: Draw 2 Fluorine atoms, showing only the valence electrons

Step #2: Share Valence Electrons in order for each atom to have 8 valence electrons.

Practice Problem:

Show a Covalent Bond between Hydrogen (H) and Chlorine (Cl)

Reactions

Synthesis Reaction

  • A synthesis reaction is a reaction in which two or more substances react to form a single substance.
  • The Reactants (Left side of Yield Sign) may be either elements or compounds.
  • The product (Right side of Yield Sign) of synthesis is always a compound.

Examples:

Review Question: What is a synthesis reaction?

Decomposition Reaction

  • A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances.
  • The reactants (Left side of Yield sign) must be a compound.
  • The products (Right side of Yield Sign) may be elements or compounds.

Examples:

Review Question: In a Decomposition reaction, what must the reactions always be?

Single Replacement Reaction

  • This is a reaction in which one element takes the place of another element in a compound.

Examples:

In the above reaction (Cu) takes the place of (Ag). Therefore this is a Single Replacement Reaction.

Review Question: What is a Single Replacement Reaction?

Double Replacement Reaction

  • This is a reaction in which two different compounds exchange positive ions and form two new compounds.

Examples:

In The above reaction (I) Replaces () and () Replaces (I). Therefore this is a Double Replacement Reaction.

Review Question:

What is a Double Replacement Reaction.

Remember, in addition to this study guide, you also must review any class notes and the text book.

The pages in the text book to pay particular attention to are:

Pages 159-197 (Bonding)

Pages 199-203 (Reactions)