Periodic Trends
What is the trend in atomic radius as you move down a group in the periodic table?
Atomic radius increases down a group due to the addition of electron shells.
What type of bond is formed when electrons are shared between atoms?
A covalent bond is formed when electrons are shared between atoms.
What is the molecular geometry of methane (CH₄)?
The molecular geometry of methane (CH₄) is tetrahedral.
What does VSEPR stand for and what is its purpose?
VSEPR stands for Valence Shell Electron Pair Repulsion; it predicts molecular shapes based on electron pair repulsion.
What determines whether a molecule is polar or nonpolar?
Polarity is determined by the difference in electronegativity between bonded atoms and the molecular geometry.
Describe how electronegativity changes across a period from left to right.
Electronegativity increases from left to right due to increasing nuclear charge.
Describe the difference between ionic and covalent bonds.
Ionic bonds involve the transfer of electrons, while covalent bonds involve the sharing of electrons.
How does the presence of lone pairs affect molecular shape?
Lone pairs repel more strongly than bonding pairs, altering the molecular shape.
Using VSEPR theory, predict the shape of the water molecule (H₂O).
The shape of water (H₂O) is bent due to two lone pairs on the oxygen atom.
Provide an example of a polar molecule and explain why it is polar.
An example of a polar molecule is hydrochloric acid (HCl) because of the difference in electronegativity between hydrogen and chlorine.
Define ionization energy and explain how it varies down a group.
Ionization energy is the energy required to remove an electron; it generally decreases down a group and increases across a period.
What is the role of hybridization in bond formation?
Hybridization mixes atomic orbitals to form new hybrid orbitals for bonding.
Describe the geometry of a molecule with a trigonal bipyramidal electron geometry.
A molecule with a trigonal bipyramidal electron geometry has a corresponding molecular geometry of either trigonal bipyramidal or seesaw, depending on lone pairs.
What is the electron geometry and molecular geometry of a molecule with the formula AB₂E₂?
AB₂E₂ has a tetrahedral electron geometry and a bent molecular geometry.
How do molecular geometry and electronegativity contribute to molecular polarity?
Molecular geometry affects polarity; asymmetrical shapes with polar bonds result in polar molecules.
What are the trends in metallic character as you move across a period?
Metallic character decreases across a period from left to right and increases down a group.
Explain the concept of resonance and provide an example.
Resonance occurs when a molecule can be represented by two or more valid Lewis structures; e.g., benzene (C₆H₆).
What is the difference between a tetrahedral and a trigonal planar molecular geometry?
Tetrahedral geometry has four bonding pairs, while trigonal planar has three bonding pairs and no lone pairs.
Explain the significance of the steric number in determining molecular shape.
The steric number is the sum of bonded atoms and lone pairs and helps determine the molecular shape.
What is dipole moment and how is it measured?
Dipole moment is a measure of the separation of positive and negative charges; it is measured in Debye units (D).
Explain the significance of effective nuclear charge in relation to periodic trends.
Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom, influencing atomic size and ionization energy.
Discuss the factors that influence bond length and bond strength.
Factors influencing bond length and strength include atomic size, bond order, and electronegativity differences.
Explain how molecular geometry relates to the polarity of a molecule.
Molecular geometry affects polarity; for example, a bent shape can lead to a polar molecule.
Describe how VSEPR theory accounts for the shape of sulfur tetrafluoride (SF₄).
Sulfur tetrafluoride (SF₄) has a seesaw shape due to the presence of one lone pair.
Explain how the presence of polar bonds can lead to a nonpolar molecule with symmetrical geometry.
A symmetrical molecule with polar bonds can be nonpolar, like carbon dioxide (CO₂), because the dipoles cancel out.