Textbook Question
How many valence shell electrons do each of the following elements contain? How many new bonds can each form?
(a) C
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1. A Review of General Chemistry
Bonding Preferences
4:21 minutesProblem 49c
Textbook Question
Draw in all missing lone pairs for the following molecules.
(c) 
Verified step by step guidance1
Step 1: Identify the molecule shown in the image. The structure represents a ketone functional group, specifically 2-propanone (acetone). The central carbon is double-bonded to an oxygen atom and single-bonded to two methyl groups.
Step 2: Recall that oxygen typically has six valence electrons. In this structure, two of these electrons are involved in the double bond with carbon, leaving four electrons to form lone pairs.
Step 3: Add two lone pairs to the oxygen atom. These lone pairs should be placed symmetrically around the oxygen atom to reflect its tetrahedral electron geometry.
Step 4: Verify that the central carbon atom has a complete octet. The carbon is bonded to two methyl groups and the oxygen atom via a double bond, satisfying the octet rule.
Step 5: Confirm that all other atoms in the molecule (hydrogens and carbons) have the correct number of bonds and no lone pairs are needed for them. Hydrogen atoms are always single-bonded, and the methyl groups are fully saturated.
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Video duration:
4mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lone Pairs
Lone pairs are pairs of valence electrons that are not involved in bonding and are localized on a single atom. In organic chemistry, recognizing lone pairs is crucial for understanding molecular geometry, reactivity, and the overall electronic structure of molecules. They can influence the polarity and hydrogen bonding capabilities of a compound.
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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 provide a visual representation of the arrangement of electrons, helping to predict molecular shape and reactivity. Drawing Lewis structures accurately is essential for identifying missing lone pairs in a given molecule.
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Valence Shell Electron Pair Repulsion (VSEPR) Theory
VSEPR theory is a model used to predict the geometry of individual molecules based on the repulsion between electron pairs in the valence shell of the central atom. According to this theory, electron pairs, including lone pairs, will arrange themselves to minimize repulsion, which is key to understanding the three-dimensional shape of molecules and the placement of lone pairs.
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