Textbook Question
Which of the following alkali metal halides has the largest lat-tice energy? Explain.(a) (b) (c)
Ch.7 - Covalent Bonding and Electron-Dot Structures
Chapter 7, Problem 33
Two electrostatic potential maps are shown, one of methyl-lithium (CH3Li) and the other of chloromethane (CH3Cl). Based on their polarity patterns, which do you think is which? (a)
(b)
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Identify the elements in each molecule: CH3Li (methyl-lithium) and CH3Cl (chloromethane).
Understand the concept of electronegativity: Chlorine (Cl) is more electronegative than Carbon (C), and Carbon is more electronegative than Lithium (Li).
Analyze the electrostatic potential maps: Red regions indicate areas of negative charge (high electron density), while blue regions indicate areas of positive charge (low electron density).
Compare the maps: In map A, the red region is around the carbon atom, indicating a higher electron density near carbon. In map B, the red region is around the chlorine atom, indicating a higher electron density near chlorine.
Conclude the identification: Map A corresponds to CH3Li (methyl-lithium) because the carbon is more electronegative than lithium, and map B corresponds to CH3Cl (chloromethane) because chlorine is more electronegative than carbon.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrostatic Potential Maps
Electrostatic potential maps visually represent the distribution of electron density in a molecule, indicating areas of positive and negative charge. These maps use color gradients, where red typically indicates regions of high electron density (negative potential) and blue indicates low electron density (positive potential). Understanding these maps is crucial for analyzing molecular polarity and predicting reactivity.
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Kinetic & Potential Energy
Polarity of Molecules
Polarity in molecules arises from differences in electronegativity between atoms, leading to uneven distribution of electron density. Polar molecules have a significant dipole moment due to the presence of polar bonds, which can affect their physical properties and interactions. Recognizing the polarity of methyl-lithium and chloromethane is essential for interpreting their electrostatic potential maps.
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Comparison of Methyl-Lithium and Chloromethane
Methyl-lithium (CH3Li) is an organolithium compound that exhibits significant ionic character, making it highly polar, while chloromethane (CH3Cl) is a polar covalent molecule due to the electronegativity difference between carbon and chlorine. Analyzing the electrostatic potential maps allows for distinguishing between these two compounds based on their charge distributions and polarity patterns.
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Related Practice
Textbook Question
The following diagram shows the potential energy of two atoms as a function of internuclear distance. Match the descriptions with the indicated letter on the plot.(a) Repulsive forces are high between the two atoms. (b) The two atoms neither exert attractive nor repulsive forces on one another.(c) The attractive forces between atoms are maximized, resulting in the lowest energy state.(d) Attractive forces between atoms are present but are not at maximum strength.
Textbook Question
The following diagram shows the potential energy of two atoms as a function of internuclear distance. Which bond is the strongest? Which bond is the longest?
Textbook Question
Electrostatic potential maps of acetaldehyde (C2H4), ethane (C2H6), ethanol (C2H6O), and fluorethane (C2H5F) are shown. Which do you think is which? (a)
(b)
(c)
(d)
Textbook Question
Characterize bonds between the two atoms as covalent or ionic.(a) Cl and F(b) Rb and F(c) Na and S (d) N and S
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Textbook Question
The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple. (Red = O, gray = C, blue = N, ivory = H). Give the formula of thalidomide, and indicate the positions of multiple bonds and lone pairs.