11/4 what are lewis structures? - part ii

Launch: 11/4   Grab your binder and immediately take a seat!

  Place homework (practice questions) on desk

1.  Draw the correct Lewis structures for the following atoms. Be sure to use the 3-steps!

i.  Br2

ii.  H2S iii.  CCl4

Schedule   We have an exam in 6 days!

  We don’t have time to waste!   Follow our 7 class rules

  You may not use inappropriate language

  If you have a question, ask!

What are Lewis structures? – Part II

Mr. Heffner 11/4/09

  Lewis structures are…   pictures of covalent molecules

  nonmetal and nonmetal share to get 8

F •  •  •  •  •  •  -

What are Lewis structures?

Lewis Structure

F •  •  •  • 

•  •  Covalent Bond

(dash = 2 electrons)

8 =

What are Lewis structures?

 Cocaine  C17H21NO4

Double Bond 2 dashes = 4 electrons

What are Lewis structures?   Large biological molecules are made of

  carbon (C) – 4 bonds   nitrogen (N) – 3 bonds

  oxygen (O) – 2 bonds   hydrogen (H) – 1 bond

  To fill octet C, N, & O sometimes form double/triple bonds   H, I, Br, Cl and everything else = only single bonds

What is a Lewis structure?   There is a 3-step process for creating Lewis

structures: 1.  Draw Lewis symbols & count dots 2.  Arrange atoms so they have a full octet

  If necessary form a double/triple bond

3.  Count dots & make bonds

Example Draw the Lewis structure for O2

  Step 1: Draw Lewis symbols & count dots

O •  •  • 

•  •  •  12 dots

O •  • 

•  • 

•  • 

Example Draw the Lewis structure for O2

  Step 2: Arrange atoms so they have a full octet

7 = 7 =

O •  •  •  •  •  •  O

•  • 

•  • 

•  • 

Example Draw the Lewis structure for O2

  Step 2: Arrange atoms so they have a full octet

8 = 8 =

O •  •  • 

•  •  •  O

•  • 

•  • 

•  • 

•  • 

•  •  • 

Example Draw the Lewis structure for O2

  Step 3: Count dots & make bonds

O •  •  •  •  •  O • 

•  •  • 

Double Bond 2 dashes = 4 electrons 12 dots

Example Draw the Lewis structure for N2

Whiteboards   Work in pairs

  Trade-off marker every question

  You have 60 seconds to draw the answer   Show all three steps!

  Lift board only when prompted

CCl4

CO2

CH2Cl2

N2

Molecular Models   Work with partner

1.  draw all the Lewis symbols 2.  draw the correct Lewis structure

3.  build a model using toothpicks and candy 4.  draw a picture of your model (label the atoms) 5.  identify the types of bonds present in molecule

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Step 1 Step 2 Step 3

Exit Slip 1.  The bonds in water (H2O) are

a.  single bonds b.  ionic bonds

c.  triple bonds d.  double bonds

Exit Slip 2.  The correct Lewis structure for CO2 is

Exit Slip 3.  Which of the following molecules contains a

covalent triple bond? a.  C2H2 b.  I2 c.  NH3

d.  N2

Exit Slip 4.  Bubble in A

Then, draw the Lewis structure for SiF4

Exit Slip 5.  Bubble in A

Then, draw the Lewis symbol for O2

Homework   Finish Lewis symbol and ions worksheet