Q: How do you calculate the formal charge on an atom in a Lewis structure?

$\text{Formal charge} = (\text{valence electrons}) - (\text{nonbonding electrons}) - \frac{1}{2}(\text{bonding electrons})$

Q: Which of the following statements about $ ext{NH}_3$ is correct?

$\text{NH}_3$ has a trigonal pyramidal molecular geometry due to one lone pair on nitrogen.

Q: Which of the following best describes the process for calculating the effective nuclear charge ($Z_{\text{eff}}$) for a 2p electron in a nitrogen atom?

$Z_{\text{eff}} = Z - S$, where $Z$ is the atomic number and $S$ is the number of core electrons (not valence electrons).

Q: Which of the following statements about $ ext{pi}$ bonds is true?

$\text{Pi}$ bonds must involve unhybridized p orbitals.

Question 1

Which of the following correctly explains why the atomic radius decreases as you move from left to right across a period in the periodic table?

Accepted Answer

The number of protons increases, which increases the effective nuclear charge, pulling electrons closer to the nucleus.

Question 2

When writing the electron configuration for a transition metal cation, which electrons are removed first?

Accepted Answer

Electrons from the highest principal quantum number (n), typically the s orbital.

Question 3

Which of the following molecules has a trigonal planar electronic geometry?

Accepted Answer

BF$_3$

Question 4

Which factor most strongly influences the stability of an ionic compound?

Accepted Answer

The magnitude of the lattice energy, which increases with higher charge and smaller ionic radii.

Question 5

How do you calculate the formal charge on an atom in a Lewis structure?

Accepted Answer

$	ext{Formal charge} = (	ext{valence electrons}) - (	ext{nonbonding electrons}) - \frac{1}{2}(	ext{bonding electrons})$

Question 6

Which bond angle is expected for a molecule with tetrahedral geometry?

Accepted Answer

$109.5^\circ$

Question 7

Which of the following statements about $	ext{NH}_3$ is correct?

Accepted Answer

$	ext{NH}_3$ has a trigonal pyramidal molecular geometry due to one lone pair on nitrogen.

Question 8

Which of the following will result in the largest lattice energy for an ionic compound?

Accepted Answer

A compound with small ions and high charges, such as MgO.

Question 9

Which of the following best describes the process for calculating the effective nuclear charge ($Z_{	ext{eff}}$) for a 2p electron in a nitrogen atom?

Accepted Answer

$Z_{	ext{eff}} = Z - S$, where $Z$ is the atomic number and $S$ is the number of core electrons (not valence electrons).

Question 10

As you move from left to right across a period, which property generally increases?

Accepted Answer

Electronegativity

Question 11

Which of the following molecules contains a triple bond?

Accepted Answer

N$_2$

Question 12

Which statement about $	ext{sp}^2$ hybridization is correct?

Accepted Answer

It results in a trigonal planar geometry with $120^\circ$ bond angles.

Question 13

Which of the following statements about $	ext{pi}$ bonds is true?

Accepted Answer

$	ext{Pi}$ bonds must involve unhybridized p orbitals.

Question 14

Which of the following best explains why double and triple bonds are shorter and stronger than single bonds?

Accepted Answer

Multiple bonds increase electron density between atoms, increasing bond strength and decreasing bond length.

Question 15

Which of the following best describes ionization energy?

Accepted Answer

The energy required to remove one electron from a gaseous atom.

Question 16

Which statement is true regarding the formation of a dipole moment in a molecule?

Accepted Answer

A dipole moment forms when there is an uneven distribution of electron density due to differences in electronegativity.

Question 17

Which of the following is the correct order for constructing a Lewis structure?

Accepted Answer

Count total valence electrons, place the least electronegative atom in the center, connect atoms with single bonds, assign remaining electrons to complete octets.

Question 18

Which of the following molecules is expected to have a square planar molecular geometry?

Accepted Answer

XeF$_4$

Question 19

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures represent different possible arrangements of electrons, not atoms.

Question 20

Which of the following best describes delocalized $	ext{pi}$ bonding?

Accepted Answer

Delocalized $	ext{pi}$ bonding occurs when electron density is spread over several atoms, as in benzene.

General Chemistry: Atomic Structure, Bonding, and Molecular Geometry – Exam 4 Review Key Takeaways

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