Molecular Structure and Geometry Flashcards
To learn how to construct and interpret molecular structures using Lewis diagrams and resonance, and to analyze the geometry of molecules, including how molecular symmetry affects polarity.
What does a Lewis structure represent?
Think about how a molecule’s electrons are arranged in a Lewis structure
The arrangement of valence electrons in a molecule.
Lewis structures include bonding pairs and lone pairs of electrons, helping predict molecular shapes and reactivity.
What is the bond angle in a tetrahedral molecule?
Focus on a molecule with four electron pairs around the central atom.
109.5 degrees.
Methane (CH₄) is a classic example of a molecule with tetrahedral geometry.
What is resonance?
Think in molecules that can be represented by more one Lewis structure
Resonance is a concept where a molecule cannot be accurately represented by a single Lewis structure, but instead by two or more contributing structures (resonance forms). These forms depict the delocalization of electrons across multiple atoms
An example is the carbonate ion (CO₃²⁻), where the double bond is delocalized between the oxygen atoms, and the true structure is a hybrid of the resonance forms.
How do you identify a polar molecule?
Focus on the molecular shape and the distribution of electron density.
Polar molecules have an unequal distribution of charge and asymmetrical shape.
Water (H₂O) is polar because of its bent shape, creating a net dipole moment.
How does molecular symmetry affect polarity?
Consider how symmetrical shapes affect the distribution of charges.
Symmetrical molecules tend to be nonpolar.
Symmetry causes the dipoles to balance, resulting in no net dipole momen
Molecules like carbon dioxide (CO₂) are nonpolar because the dipoles cancel out due to the linear, symmetrical shape.
