Chem 1211 Central Georgia Technical College Name _______________________________________
Chemistry 1: Lab #8
Lab Group # ______________
Building Molecular Models Instructor’s initials: _____________
Purpose: To construct models of molecules containing single, double, and triple bonds: draw the structural formulas and draw the Lewis dot structures.
Equipment needed: Molecular modeling kit for each lab group.
Introduction:
Number of bonding groups attached to the central atom | Number of lone pairs on the central atom | Number of electron clouds on the central atom | Electron pair geometry | Molecular geometry |
---|---|---|---|---|
A total of only two atoms | Any number on either atom | No central atom | Linear | |
2 | 0 | 2 | Linear | Linear |
3 | 0 | 3 | Trigonal planar | Trigonal planar |
2 | 1 | 3 | Trigonal planar | Bent |
4 | 0 | 4 | Tetrahedral | Tetrahedral |
3 | 1 | 4 | Tetrahedral | Trigonal Pyramidal |
2 | 2 | 4 | Tetrahedral | Bent |
5 | 0 | 5 | Trigonal Bipyramid | Trigonal Bipyramid |
4 | 1 | 5 | Trigonal Bipyramid | See-Saw |
3 | 2 | 5 | Trigonal Bipyramid | T-Shaped |
2 | 3 | 5 | Trigonal Bipyramid | Linear |
6 | 0 | 6 | Octahedral | Octahedral |
5 | 1 | 6 | Octahedral | Square pyramid |
4 | 2 | 6 | Octahedral | Square Planar |
Procedure: adapted for on-line classes during the COVID-19 closure of CGTC
- A molecular model kit was used to build a model of each of the following molecules. Observe the picture. Sketch the model (as best you can) showing its three-dimensional structure. Notice in the example that each circle representing a ball has the symbol of the element in it.
- Draw the Lewis dot structure corresponding to the structural formula. Complete the octet by surrounding each atom with 8 electrons (except for hydrogen which only gets 2). The pictures of the molecular models have a wooden peg (without a wooden ball at the end) to indicate the position of a lone pair of electrons.
- Draw the structural formula corresponding to the molecular model and the Lewis structure.
- Verify each structure by identifying the number of bonds, bonding groups, lone pairs, and charge clouds on each central atom. Identify the shape & polarity of each molecule. Check electronegativity values. More electronegative = negative end of the bond. Electronegativity tells you the polarity of the bond buy you need to find the polarity of the molecule for this assignment.
Data:
Molecular Formula: | Sketch:Make sure elements are labeled | Lewis Dot Structure: | Structural Formula: | Numbers: | Geometry & Polarity : |
---|---|---|---|---|---|
Molecules with only Single Bonds | |||||
Example: HOCl Valence electrons: _14_ | H Cl | H – O | Cl | (on the O) Bonds: _2_ Bonding Groups: _2_ Lone Pr: _2__ Clouds: __4_ | Bent Polar molecule | |
H2 Valence electrons: ______ | (on either) Bonds: ____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
Cl2 Valence electrons: ______ | (on either) Bonds: ____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
HBr Valence electrons: ______ | (on Br) Bonds: ____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
CH2Cl2 Valence electrons: ______ | (on C) Bonds: ____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
N2H4 Valence electrons: ______ | (on N) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
NH2OH Valence electrons: ______ | N central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ O central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | N central: O central: | |||
Molecules with a Double Bond | |||||
C2H4 Valence electrons: ______ | (on C) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
C2H3Cl Valence electrons: ______ | (on C) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
HCOOH Valence electrons: ______ | C central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ O central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | C central: O central | |||
Molecules with a Triple Bond | |||||
N2 Valence electrons: ______ | (on either) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
C2H2 Valence electrons: ______ | (on C) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | ||||
HOCN Valence electrons: ______ | C central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ O central: Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ | C central: O central | |||
Try this: (note that there are at least two possible structures) | |||||
C3H4 Valence electrons: ______ | (for a C) Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ or Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ or Bonds: _____ Bonding Groups: ____ Lone Pr: ____ Clouds: ____ |
Pictures: only Single bonds, p. 1: only Single bonds, p. 2: Double bonds:
Triple bonds: Try this:
White – Hydrogen
Black – Carbon
Green – Chlorine
Orange – Bromine
Blue – Nitrogen
Red – Oxygen
Questions:
- In your own words, define the following terms:
- Covalent bond
- Double bond
- Octet rule
- Structural formula
- Electron
- Valence electrons
- What do each of the following represent in the molecular model kit?
- A rigid connector that is not attached to an atom at one end
- A rigid connector with an atom at each end
- Two flexible connectors (springs) holding two atoms together
- Determine the “molecular geometry” of each of the following molecules: (the bold atom is central)
- H2S
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- PH3
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- SiH4
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- CS2
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- SO2
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Seeley, Dale. Unpublished material. Central GA Technical College. 2018.