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Questions and Answers
According to VSEPR theory, what principle governs the shape of molecules?
According to VSEPR theory, what principle governs the shape of molecules?
- Valence electron pairs repel and seek maximum separation. (correct)
- Molecules align to minimize nuclear repulsion.
- Atoms arrange themselves to maximize electron pair proximity.
- Electron pairs attract each other, forming compact shapes.
Molecules with polar covalent bonds are always polar molecules.
Molecules with polar covalent bonds are always polar molecules.
False (B)
What is the approximate bond angle in a molecule with tetrahedral geometry, according to the VSEPR theory?
What is the approximate bond angle in a molecule with tetrahedral geometry, according to the VSEPR theory?
109.5
The ability of an atom to attract electrons in a chemical bond is called its ______.
The ability of an atom to attract electrons in a chemical bond is called its ______.
Match the following molecules with their polarity:
Match the following molecules with their polarity:
Based on the provided electronegativity values, which of the following bonds would be considered the MOST polar covalent bond?
Based on the provided electronegativity values, which of the following bonds would be considered the MOST polar covalent bond?
Dispersion forces decrease with increasing molecular mass.
Dispersion forces decrease with increasing molecular mass.
What approximate electronegativity difference between two atoms is generally indicative of an ionic bond?
What approximate electronegativity difference between two atoms is generally indicative of an ionic bond?
In predicting molecular shapes, a double or triple bond is treated as a ______ bond.
In predicting molecular shapes, a double or triple bond is treated as a ______ bond.
Match the compound with its molecular shape.
Match the compound with its molecular shape.
Which of the following statements correctly describes the nature of hydrogen bonds?
Which of the following statements correctly describes the nature of hydrogen bonds?
Considering electronegativity differences, which of the following molecules would exhibit dipole-dipole forces?
Considering electronegativity differences, which of the following molecules would exhibit dipole-dipole forces?
The strength of a hydrogen bond is approximately equal to the strength of a typical covalent bond.
The strength of a hydrogen bond is approximately equal to the strength of a typical covalent bond.
Flashcards
VSEPR Theory
VSEPR Theory
A theory stating that electron pairs around an atom repel each other, influencing molecular shape.
Tetrahedral Angle
Tetrahedral Angle
An angle of approximately 109.5° formed between electron pairs in a tetrahedral arrangement.
Polar Covalent Bonds
Polar Covalent Bonds
Covalent bonds where electrons are unequally shared between atoms.
Dipole
Dipole
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Electronegativity
Electronegativity
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Nonpolar Covalent Bond
Nonpolar Covalent Bond
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Ionic Bond
Ionic Bond
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Dipole-Dipole Forces
Dipole-Dipole Forces
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Dispersion Forces
Dispersion Forces
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Hydrogen Bond
Hydrogen Bond
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Multiple Bonds & Shape
Multiple Bonds & Shape
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Study Notes
- Electron Dot structures indicate the number of covalent bonds in a molecule but not the shape.
VSEPR Theory
- The Valence Shell Electron Repulsion (VSEPR) theory states that electron pairs repel each other, therefore molecules adjust to maximize the distance between valence electron pairs.
- Tetrahedral bonding results from VSEPR, creating a tetrahedral angle of approximately 109.5°.
Polar Covalent Bonds
- Electrons are shared evenly between the same type of atoms (ex: H2, O2, Cl2)
- Electrons are not shared evenly in heteroatomic molecules (ex: HCl, H2O, NH3).
- The symbol 𝛿 (delta) signifies a small amount of charge at an end of a molecule.
- Covalent bonds with unequal sharing of electrons are polar covalent bonds.
- A dipole is a pair of equal and opposite charges separated in space (ex: H-Cl).
- Polar molecules have a net dipole.
- In tetrahedrally shaped molecules, slightly polar bonds can cancel each other out, resulting in a non-polar molecule (net zero dipole).
Electronegativity
- Electronegativity refers to an atom's power to attract electrons.
- Electronegativity increases from left to right across the periodic table.
- Electronegativity decreases from top to bottom on the periodic table.
- The atom with the highest electronegativity in a polar molecule carries the slightly negative charge.
- Electronegativity differences determine bond type:
- 0.0 - 0.4: Covalent (nonpolar), e.g., H-H (0.0)
- 0.4 - 1.0: Covalent (slightly polar), e.g., H-Cl (0.9)
- 1.0 - 2.0: Covalent (very polar), e.g., H-F (1.9)
- ≥ 2.0: Ionic, e.g., NaCl (2.1)
- Polar molecules align, affecting substance properties.
Dispersion Forces
- Dispersion forces are weak intermolecular forces between pairs of molecules.
- These forces arise from the attraction of one molecule's nucleus to the electron cloud of a neighboring molecule.
- Repulsion between the two electron clouds opposes this attraction, thus the resulting force is very small.
- Dispersion force strength increases with molecular mass.
Hydrogen Bonding
- It is an intermolecular attraction when a slightly positive hydrogen atom is attracted to an unshared electron pair in a nearby molecule.
- Hydrogen bond strength is about one-tenth of a normal covalent bond.
Predicting Shapes of Molecules
- Common molecular shapes include linear, trigonal planar, bent, tetrahedral, pyramidal, trigonal bipyramidal, and octahedral.
Compounds with Double or Triple Bonds
- Double and triple bonds are treated as a single bond when determining molecule shape.
- Carbon dioxide (CO2): linear
- Hydrogen cyanide (HCN): linear
- Methanal (CH2O): Trigonal Planar
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Description
This content explains VSEPR theory, including how molecules adjust to maximize distance between valence electron pairs, resulting in shapes such as tetrahedral. It also describes polar covalent bonds, dipoles, and how molecular shape affects polarity.
