INTRODUCTION TO CHEMICAL BONDING

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INTRODUCTION TO CHEMICAL BONDING

• By F. Todd 2004

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1. WHERE ARE ELECTRONS PLACED IN AN ATOM?

• IN THE ELECTRON CLOUD WHICH SURROUNDS THE NUCLEUS

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• A. ELECTRON CLOUD
• 1. THE CLOUD GIVES THE ATOM ITS
• BASIC SHAPE
• 2. IT GIVES THE ATOM ITS CHEMICAL PROPERTIES.

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• B. ENERGY LEVELS
• They are layers in the electron cloud where the
  electrons are located.
• Level 1 holds 2 electrons K shell
• Level 2 holds 8 electrons L shell
• Level 3 holds 18 electrons M shell
• The outer most energy level is called the valence
  energy level. THE VALENCE LEVEL CANNOT HOLD MORE
  THAN 8 ELECTRONS

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2. WHAT IS A MOLECULE?

• 1. SMALLEST PARTICLE OF A COMPOUND THAT HAS ALL
  THE PROPERTIES OF THAT COMPOUND

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3. WHAT IS A CHEMICAL BOND?

• 1. ATTACHMENT BETWEEN TWO ATOMS THAT JOIN THEM
  TOGETHER
• 2. THE ATOMS ARE HELD TOGETHER THROUGH EITHER A
  SHARING OR TRANSFER OF ELECTRONS.
• 3. ELECTRICAL ATTRACTIONS BETWEEN THE ATOMS HOLD
  THEM TOGETHER IN A CHEMICAL BOND.

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4. WHAT IS A STABLE ATOM?

• 1. ATOMS WHOSE VALENCE ENERGY LEVEL IS COMPLETE
  OR FILLED WITH THE MAXIMUM NUMBER OF ELECTONS IT
  CAN HOLD.

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DO HAPPY/SAD ATOM WORKSHEET NOW.
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5. WHAT ATOMS COMBINE?

• 1. ATOMS THAT COMBINE ARE LOOKING TO HAVE THEIR
  VALENCE ENERGY LEVEL COMPLETE.
• 2. DIATOMIC MOLECULES MOLECULES MADE OF ONLY 2
  ATOMS
• Ex. H2, O2, HF

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Covalent Bonding 1. What is a covalent Bond?

• Attraction between atoms created as a result of
  atoms sharing valence electrons.
• This bond is usually formed between nonmetals
• In this bond, both atoms attract the shared
  electrons at the same time.
• Example H2, (ball example), Cl2, H2O

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2. FORMING A COVALENT BOND -WATER MOLECULE
EXAMPLE -Conditions must be right (dance
example) -Both oxygen and hydrogen are
happy/stable
O
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Electrons spend equal time around both Hydrogen
nuclei
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• A. POLAR COVALENT BOND- Unequal sharing of
  electrons (H2O, HF)

Electrons spend more time around the Fluorine
nuclei. Gives Hydrogen a slight charge and
Fluorine a slight - charge
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IONIC Bonding 1. What is an Ionic Bond?

• Attraction between charged atoms called ions that
  is created when valence electrons are
  transferred between atoms.
• This bond is usually formed between a metal and a
  nonmetal.
• Ion an atom or group of atoms that have become
  electrically charged by gaining or losing
  electrons.
• Example NaCl, CaCl2,

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2. FORMING AN IONIC BOND -NaCl EXAMPLE
Chlorine receives the 1 electron And becomes a -1
ion.
Sodium transfers 1 electron And becomes a 1 ion.
-1
1
Cl
OPPOSITE CHARGES ATTRACT!!!!
--Both Sodium and Chlorine are happy/stable
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WATER

• Water is a compound molecule.
• Formula H2O
• Water molecules have oppositely charged ends.
  This makes water a polar molecule.
• Held together by a polar covalent bond.

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• Water is cohesive Water molecules stick to each
  other by hydrogen bonds

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• These hydrogen bonds are very important.
• Allows water to freeze at 32oF (0oC)
• Allows water to boil at 212oF (100oC)
• If water did NOT have these hydrogen bonds it
  would make life impossible.
• Water would boil at -112oF (-80oC)
• Water would freeze at -148oF (-100oC)

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• This cohesive property can create a rubbery
  skin on the surface called surface tension.

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• Water is adhesive Water molecules stick to
  other substances by hydrogen bonds.

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