Lab#7

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Adelphi University *

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109

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Chemistry

Date

Dec 6, 2023

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pdf

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Uploaded by DeanComputer2273

Names: _________________________________________ Group #: _______________ Molecular Models Learning outcomes: By the end of this activity, students will be able to: ● Explain the difference between paired and unpaired electrons in a Lewis Dot Structure of an atom. ● Determine the number of bonds an atom can form using a Lewis Dot Structure of an atom. ● Draw a Lewis Structure of a compound when provided the formula of the compound, based upon the number of bonds each atom can form. ● Explain the difference between Lewis Structures and Stick Structures in how they represent a molecule’s structure. ● Define what a functional group is and their function in structures. ● Recognize the following functional groups when provided a structure in Lewis Structure format or Stick Structure format: ○ Alcohol ○ Primary Amine ○ Quaternary Amine ○ Carboxylic Acid ○ Carboxyl ○ Carboxylic Acid Salt ○ Thiol ○ Phenyl ○ Phenol ○ Ester ○ Amide

Model 1: Review - Lewis Dot Structures and Bonding Core valence models and Lewis Dot structures are both used to portray an atom, however they differ in terms of what information is being presented. Figures 1A-1D below show oxygen on the periodic table, the core valence model for oxygen, the Lewis Dot structure of oxygen and a molecule of water showing how many bonds oxygen forms. Figure 1A: Oxygen on the periodic table Figure 1B: Core valence model of oxygen Figure 1C: Lewis Dot structure of an oxygen atom Figure 1D: Lewis Structure of a water molecule showing oxygen bonding Using Figures 1A-1D, answer the following questions: 1. According to the fig.1B, Core Valence Model of oxygen, how many valence electrons does oxygen have? 1

2. Consider the placement of oxygen on the periodic table. How does this quantity of valence electrons relate to the location of oxygen on the periodic table? 3. Examin fig. 1C, how many electrons are being represented in the Lewis Dot Structure? 4. Based upon your answers for questions 1 and 3, what is being represented by the dots in a Lewis Dot Structure. 5. In a Lewis Dot structure you have pairs of electrons and unpaired electrons. Paired electrons are sides of your Lewis Dot structure that have 2 dots forming a pair, whereas unpaired electrons are when you have a side of the Lewis Dot structure with 1 dot. a. How many pairs of electrons does the Lewis Dot structure of oxygen have? b. How many unpaired electrons does the Lewis Dot structure of oxygen have? 6. Compare Figures 1C and 1D, the Lewis Dot of oxygen and oxygen in a water molecule. a. How many bonds did oxygen form with other atoms in the water molecule? b. Which electrons, paired or unpaired, did the oxygen use to form the bonds with the other atoms? c. Based upon your answer for 6 a and b above, how can you predict the number of bonds an atom will form from the Lewis Dot Structures? 2

Model 2: Representing Molecules: Lewis Structures and Stick Structures Lewis Structures and Stick Structures are two ways in which the structure of a molecule can be represented, however these two representations differ in how much information is being presented. Below is the molecular formula and the Lewis Structure and Stick Structure of Propane. Molecular Formula of Propane: C 3 H 8 Figure 2A: Lewis Structure of Propane Figure 2B: Stick Structure of Propane Use the molecular formula and Figures 2A and 2B to answer the following questions. 1. Draw the Lewis Dot structures for the following atoms: a. Carbon b. Hydrogen 2. Based upon the Lewis Dot structures you drew above, determine the number of bonds each of the following atoms would form: a. Carbon b. Hydrogen 3. Examine the Lewis Structure of Propane in Fig. 2A: a. Is each carbon fulfilled with the number of bonds determined in question 2 above? b. Is each hydrogen atom fulfilled with the number of bonds determined in question 2 above? 4. Compare the Lewis structure of propane, Fig 2A, to the molecular formula of propane. What does the Lewis Structure show you that the molecular formula does not? 3

5. The Lewis Structure in Fig 2A and the Stick Structure in 2B are both representing propane with the molecular formula C3H8. Compare the Stick structure to the Lewis Structure to see the difference in representations. a. What element is being represented by the ending points of each line and the intersection point of the lines? b. What do each of the lines in the stick structure represent? c. What element is not shown or represented at all in this stick structure? 6. Summarizing the information: Complete the table below to summarize what is being represented by a molecular formula, lewis structure and stick structure. Table 1: Summarization of Molecular Representations Molecular Representation What is being shown in this representation of the molecule? Molecular Formula Lewis Structure Stick Structure 4

Figure 2C: Stick Structure of an organic molecule 7. Examine the Stick Structure in Fig 2C above. Compare this to the stick structure in Fig 2B. a. What element symbols are never written in a stick structure? b. What element symbols should always be written in a stick structure? c. When is the symbol for hydrogen written? d. When is the symbol for hydrogen not written? 5

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