Basic Molecular Structure, Octets, Resonance, and Formal Charge
What is the octet rule?
Atoms tend to form bonds so that each atom has eight electrons in its valence shell.
What is the shape of a molecule with two bonding pairs and no lone pairs on the central atom?
Linear
Which is stronger: a single bond or a double bond?
A double bond is stronger.
What type of elements form ionic bonds?
Metals and nonmetals.
What is the electronegativity trend across a period on the periodic table?
Increases from left to right.
Which atom in CO₂ has a formal charge of 0?
Both carbon and oxygen atoms have a formal charge of 0.
What is the electron geometry of NH₃?
Tetrahedral (molecular geometry is trigonal pyramidal)
Which bond is shorter: C–C or C=C?
C=C (double bond)
What is the charge on an aluminum ion?
+3
Which element has the highest electronegativity?
Fluorine
In the Lewis structure for nitrate (NO₃⁻), how many resonance structures are possible?
Three resonance structures.
What hybridization corresponds to a trigonal planar geometry?
sp²
What is the relationship between bond length and bond energy?
The shorter the bond, the higher the bond energy.
What is lattice energy?
The energy released when gaseous ions form an ionic solid.
What type of intermolecular force is strongest in water?
Hydrogen bonding
Calculate the formal charge on nitrogen in NH₄⁺.
+1
Describe the orbital overlap in a double bond.
One σ bond (head-on overlap) and one π bond (side-to-side overlap).
Rank the following bonds from weakest to strongest: N–N, N=N, N≡N.
N–N < N=N < N≡N
Rank these ionic compounds by increasing lattice energy: NaCl, MgO, KBr.
KBr < NaCl < MgO
Why does CO₂ not exhibit hydrogen bonding?
It lacks hydrogen atoms bonded to highly electronegative atoms (O, N, F).
In ozone (O₃), describe the type of bonding and resonance present.
One single and one double bond delocalized between the three oxygen atoms, creating resonance.
What is the hybridization and bond angle of the carbon in acetylene (C₂H₂)?
sp hybridization; 180° bond angle.
Explain why triple bonds have higher bond energy but shorter bond lengths.
Greater overlap of orbitals increases bond strength, pulling nuclei closer together.
Why does MgO have a higher lattice energy than NaCl?
It has higher ionic charges (+2 and –2 vs. +1 and –1) and smaller ionic radii, increasing electrostatic attraction.
Explain why ionic solids do not conduct electricity in solid form but do in molten or aqueous form.
In solids, ions are fixed in a lattice; in molten/solution form, ions are free to move and carry charge.