Bell%20Ringer4-21-09

1
Bell Ringer 4-21-09

• Period tell you _____________________.
• Group tells you _____________________.
• Draw an electron dot diagram for Br (Bromine).
• What is the octet rule?
• Show how these two atoms bond
• Ca Se ?

2
Bell Ringer 10-26-09

1. An ionic bond is a transfer of ________.
2. If an element gives up an electron, its charge is
   _______.
3. If an atom takes an electron, its charge is
   _______.
4. For an atom to be happy, it needs ______
   electrons in its outer energy level (with the
   exception of He).
5. Draw an electron dot diagram for Si (Silicon).

3
ALCOS Objectives

• 2 Describe the structure of atoms.
• 5 Differentiate between ionic and covalent
  bonds.

4
Covalent bonds

• Chapter 5
• Section 3

5
Covalent Bonds

• Co together, or sharing
• A covalent bond involves a SHARING of electrons.

6

• Covalent Bonds usually form between nonmetals.
• Recall that ionic bonds usually form between a
  metal and a nonmetal.

7
Molecule

• A molecule is a NEUTRAL group of atoms joined by
  covalent bonds.

8

• Water
• H O H

9
Double and Triple Bonds

• Double bond- chemical bond formed when atoms
  share two electrons
• O O O C O
• Triple bond- chemical bond formed when atoms
  share three electrons
• N N

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Properties of covalent bonds

• Low melting points
• Low boiling points
• Do NOT conduct electricity when dissolved in
  water

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Covalent Bond
12
Two types of covalent molecules
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Unequal Sharing of Electrons

• In a covalent bond, atoms of some elements pull
  more strongly on shared electrons than do atoms
  of other elements.

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Polar and Nonpolar covalent bonds

• Polar- Unequal sharing of electrons
• H F
• Nonpolar EQUAL sharing of electrons
• F F