Honors Chem Bonding Test

What is VSEPR theory?

Valence Shell Electron Pair Repulsion theory states that electron pairs around a central atom will arrange themselves to minimize repulsion.

How do lone pairs affect molecular shape?

Lone pairs occupy more space than bonding pairs, causing bond angles to be smaller and affecting the molecular geometry.

What is the shape of a molecule with AX₂?

Linear, with a bond angle of 180°.

What is the molecular shape of a molecule with AX₃?

Trigonal planar, with bond angles of 120°.

What shape does a molecule with AX₄ have?

Tetrahedral, with bond angles of 109.5°.

How does the presence of lone pairs affect the shape of a molecule?

Lone pairs reduce the bond angles between bonding pairs, often creating bent or angular shapes, such as in H₂O (AX₂E₂).

What are polar covalent bonds?

Bonds where electrons are shared unequally due to differences in electronegativity, resulting in partial positive and negative charges.

What is a dipole moment?

A measure of the separation of positive and negative charges in a molecule, indicating polarity.

What is the difference between polar and nonpolar molecules?

Polar molecules have an asymmetrical charge distribution, while nonpolar molecules have a symmetrical charge distribution.

How can you tell if a molecule is polar?

If the molecule has an uneven distribution of charge (asymmetrical) or contains polar bonds that do not cancel each other out, it is polar.

What is a common example of a polar molecule?

Water (H₂O), with an AX₂E₂ shape, is polar because of its bent shape and the difference in electronegativity between hydrogen and oxygen.

What is a nonpolar molecule example?

Carbon dioxide (CO₂), with an AX₂ shape, is nonpolar because it has a linear shape, and the dipoles of the C=O bonds cancel out.

What is the relationship between polarity and solubility?

Polar molecules dissolve well in polar solvents (e.g., water), while nonpolar molecules dissolve in nonpolar solvents.

What are London Dispersion Forces?

Weak intermolecular forces that occur due to temporary dipoles caused by uneven electron distribution in molecules.

What factors influence the strength of London Dispersion Forces?

Molecular size (larger molecules with more electrons have stronger LDFs) and surface area.

What is the primary intermolecular force in nonpolar molecules?

London Dispersion Forces (LDFs).

What are dipole-dipole forces?

Intermolecular forces between polar molecules where the positive end of one molecule is attracted to the negative end of another.

What is hydrogen bonding?

A strong dipole-dipole attraction that occurs when hydrogen is bonded to highly electronegative atoms like N, O, or F.

Why does water have a strong dipole moment?

Water has a bent shape (AX₂E₂) with a large electronegativity difference between oxygen and hydrogen, creating a strong dipole moment.

What is a unit cell in a crystal lattice?

The smallest repeating pattern of a crystal structure.

Why are ionic compounds like CsCl brittle?

Shifting layers of ions cause like charges to align and repel, breaking the crystal.

What is the shape of a molecule with AX₂E?

Bent, with bond angles less than 120° due to the lone pair.

What is the shape of a molecule with AX₃E?

Trigonal pyramidal, with bond angles less than 109.5° due to the lone pair.

What is the shape of a molecule with AX₄E₂?

Octahedral, with bond angles of 90° and 180°, adjusted for the lone pairs.

What is an example of a molecule with AX₃E₂?

An example is a T-shaped molecular geometry, such as chlorine trifluoride (ClF₃).

What are dipole-dipole forces?

Intermolecular forces occurring between polar molecules, where the positive end of one molecule is attracted to the negative end of another.

How do London Dispersion Forces (LDFs) arise?

They occur due to temporary dipoles caused by momentary uneven electron distribution in molecules.

What factors increase the strength of London Dispersion Forces?

Larger molecular size (more electrons) and increased molecular surface area.

Define hydrogen bonding and give an example.

A strong dipole-dipole attraction where hydrogen is bonded to highly electronegative atoms (N, O, or F). Example: H₂O.

What is a polar molecule example with AX₃?

An example is BF₃, which is nonpolar, as the dipoles cancel out due to its trigonal planar shape.

How does electronegativity affect bonding?

Differences in electronegativity between atoms determine bond polarity, with greater differences leading to more polar bonds.

What is the difference between sigma and pi bonds?

Sigma bonds form by the head-on overlap of orbitals, while pi bonds form by the sideways overlap of p orbitals.

What is the molecular geometry of AX₂?

Linear, with bond angles of 180°.

What is the molecular geometry of AX₄?

Tetrahedral, with bond angles of 109.5°.

What shape does a molecule with AX₄E have?

Trigonal pyramidal, with bond angles less than 109.5° due to the lone pair.

What is the electron geometry of AX₄?

Tetrahedral, as it accounts for both bonding and lone pairs.

What happens in resonance structures?

Resonance occurs when there are multiple valid Lewis structures for a molecule, showing delocalization of electrons.

What is the AX notation?

AX notation is a way to represent molecular shapes, where 'A' is the central atom, 'X' is the number of bonding atoms, and 'E' is the number of lone pairs.

What is the molecular geometry of AX₂E₂?

Bent, with bond angles of less than 109.5° due to the two lone pairs on the central atom.

What is the relationship between electron geometry and molecular geometry?

Electron geometry considers both bonding and lone pairs, while molecular geometry only looks at bonded atoms.

How does the steric number affect molecular geometry?

The steric number (sum of bonding pairs and lone pairs) determines the electron geometry, which in turn dictates the molecular geometry.

What is the molecular geometry of AX₃E?

Trigonal pyramidal, with bond angles less than 109.5° due to the lone pair.

How do you determine the steric number?

The steric number is the sum of bonding pairs and lone pairs on the central atom.

What is the hybridization of a molecule with AX₂?

sp hybridization, forming a linear shape.

What hybridization is expected for AX₃?

sp² hybridization, forming a trigonal planar shape.

What is the hybridization of a molecule with AX₄?

sp³ hybridization, forming a tetrahedral shape.

What causes a molecule to have a dipole moment?

A molecule has a dipole moment if it has polar bonds and an asymmetrical shape, creating a separation of charge.

What is the molecular geometry of AX₃E₂?

T-shaped, with bond angles of 90° and 180°.

What type of bonding occurs in ionic compounds?

Ionic bonds, formed by the transfer of electrons between atoms with large differences in electronegativity.

How does the AXE notation differ from molecular shape?

The AXE notation refers to the arrangement of electron pairs, while molecular shape refers specifically to the positions of atoms in a molecule.