Textbook Question
Look at the location of elements A, B, C, and D in the following periodic table:
(a) Write the formula of the simplest binary hydride of each element.
Ch.22 - The Main Group Elements
Chapter 22, Problem 14
Write electron-dot structures for each of the following molecules, and use VSEPR theory to predict the structure of each: (a) H2S (b) SO2 (c) SO3.
Verified step by step guidance1
Step 1: Determine the total number of valence electrons for each molecule. For H2S, sulfur (S) has 6 valence electrons and each hydrogen (H) has 1 valence electron, totaling 8 valence electrons. For SO2, sulfur has 6 valence electrons and each oxygen (O) has 6 valence electrons, totaling 18 valence electrons. For SO3, sulfur has 6 valence electrons and each oxygen has 6 valence electrons, totaling 24 valence electrons.
Step 2: Draw the skeletal structure of each molecule. For H2S, place sulfur in the center with hydrogen atoms bonded to it. For SO2, place sulfur in the center with oxygen atoms bonded to it. For SO3, place sulfur in the center with three oxygen atoms bonded to it.
Step 3: Distribute the remaining valence electrons to satisfy the octet rule for each atom, starting with the outer atoms. For H2S, place the remaining electrons around sulfur. For SO2, place the remaining electrons around the oxygen atoms, and if needed, form double bonds to satisfy the octet rule. For SO3, distribute electrons around the oxygen atoms and form double bonds as necessary.
Step 4: Use VSEPR theory to predict the molecular geometry. For H2S, with two bonding pairs and two lone pairs on sulfur, the shape is bent. For SO2, with two bonding pairs and one lone pair on sulfur, the shape is also bent. For SO3, with three bonding pairs and no lone pairs on sulfur, the shape is trigonal planar.
Step 5: Verify the stability of the structures by checking formal charges and ensuring that the most electronegative atoms have the negative formal charges, if any. Adjust the structures if necessary to minimize formal charges.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electron-Dot Structures
Electron-dot structures, also known as Lewis structures, represent the valence electrons of atoms within a molecule. They illustrate how electrons are shared or transferred between atoms, helping to visualize bonding and lone pairs. Each dot represents a valence electron, and lines between atoms indicate covalent bonds. Understanding these structures is essential for predicting molecular geometry and reactivity.
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Lewis Dot Structures: Ions
VSEPR Theory
Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs surrounding a central atom. According to VSEPR, electron pairs, whether bonding or lone pairs, will arrange themselves to minimize repulsion, leading to specific molecular shapes. This theory is crucial for understanding the three-dimensional arrangement of atoms in a molecule.
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Molecular Geometry
Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom, as predicted by VSEPR theory. Different geometries, such as linear, bent, or trigonal planar, influence the physical and chemical properties of the substance, including polarity and reactivity.
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