a. Draw a Lewis structure for each of the following:
b. Draw a structure for each of the species that shows approximate bond angles.
c. Which species have no dipole moment?
2. HNO₃

Verified step by step guidance

Step 1: Begin by drawing the Lewis structure for HNO3 (nitric acid). Identify the central atom, which is nitrogen (N), and arrange the surrounding atoms (hydrogen and oxygen). Nitrogen will form bonds with three oxygen atoms, and one of the oxygen atoms will be bonded to hydrogen. Distribute the valence electrons to satisfy the octet rule for each atom.

Step 2: Assign formal charges to each atom in the Lewis structure to ensure the most stable configuration. Nitrogen will have a double bond with one oxygen atom, a single bond with another oxygen atom (which is also bonded to hydrogen), and a single bond with the third oxygen atom that carries a negative charge. Use resonance structures to represent the delocalization of electrons in the nitrate group.

Step 3: To determine the approximate bond angles, consider the molecular geometry of HNO3. Nitrogen is the central atom, and the geometry around it is trigonal planar due to sp² hybridization. The bond angles around nitrogen are approximately 120°. The O-H bond angle is slightly less than 120° due to lone pair repulsion on the oxygen atom.

Step 4: Evaluate the dipole moment of HNO3. Since the molecule is asymmetrical (due to the arrangement of atoms and the presence of polar bonds), HNO3 has a net dipole moment. The polar bonds (N=O, N-O, and O-H) contribute to the overall dipole moment.

Step 5: Compare the dipole moments of other species (if provided in the problem). For a molecule to have no dipole moment, it must be symmetrical, and the bond dipoles must cancel out. HNO3 does not meet these criteria, so it has a dipole moment.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They help visualize the arrangement of electrons and the connectivity of atoms, which is crucial for predicting molecular geometry and reactivity. In the case of HNO3, understanding how to draw its Lewis structure will reveal the arrangement of nitrogen, oxygen, and hydrogen atoms.

Molecular Geometry and Bond Angles

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule, which influences its physical and chemical properties. The VSEPR (Valence Shell Electron Pair Repulsion) theory is often used to predict bond angles based on the repulsion between electron pairs. For HNO3, recognizing the geometry will help in determining the approximate bond angles between the atoms.

Dipole Moment

A dipole moment is a measure of the separation of positive and negative charges in a molecule, indicating its polarity. Molecules with an uneven distribution of electron density exhibit dipole moments, while symmetrical molecules may not. Identifying which species have no dipole moment involves analyzing their symmetry and the electronegativity of the atoms involved, which is essential for understanding their behavior in electric fields.

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