Question 1

Which of the following statements about constructing Lewis structures is CORRECT?

Accepted Answer

For polyatomic ions, you add one electron for each negative charge and subtract one for each positive charge when counting valence electrons.

Question 2

What is the correct AXE notation and molecular geometry for the carbonate ion, $$\mathrm{CO_3$^{2-}}$$?

Accepted Answer

AX3, trigonal planar

Question 3

Which molecule or ion below is expected to have a linear molecular geometry?

Accepted Answer

$$\mathrm{$$BeF_2$$}$$

Question 4

A student draws the Lewis structure for $$\mathrm{SO_2$}$$ and finds two possible structures with different locations for the double bond. What is the term for these structures?

Accepted Answer

Resonance structures

Question 5

Which of the following molecules or ions can have an expanded octet on the central atom?

Accepted Answer

$$\mathrm{PF_5$}$$

Question 6

What is the bond angle in $$\mathrm{CH_4$}$$, and what is its molecular geometry?

Accepted Answer

Bond angle: $$109.5^\circ$$, geometry: tetrahedral

Question 7

Which of the following best explains why $$\mathrm{H_2O}$$ has a bent molecular geometry rather than linear?

Accepted Answer

The two lone pairs on oxygen repel the bonding pairs, resulting in a bent shape.

Question 8

Which of the following molecules is predicted to be nonpolar based on its molecular geometry?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 9

A molecule has the formula $$\mathrm{SF_4$}. $$What is its AXE notation and molecular geometry?

Accepted Answer

AX4E1, see-saw

Question 10

Which of the following is a correct statement about the formal charge in Lewis structures?

Accepted Answer

The best Lewis structure is the one with the lowest set of formal charges, closest to zero.

Question 11

Which of the following molecules or ions has a square planar molecular geometry?

Accepted Answer

$$\mathrm{$$XeF_4$$}$$

Question 12

A patient is exposed to ozone ($$\mathrm{O_3$}) in a $$medical setting. What is the molecular geometry of ozone, and what is the approximate bond angle?

Accepted Answer

Bent, $$\u003c120^\circ$$

Question 13

Which of the following molecules or ions is expected to have a T-shaped molecular geometry?

Accepted Answer

$$\mathrm{$$BrF_3$$}$$

Question 14

Which of the following best describes the electron group geometry and molecular geometry of $$\mathrm{PF_3$}$$?

Accepted Answer

Electron group geometry: tetrahedral; molecular geometry: trigonal pyramidal

Question 15

Which of the following molecules or ions is expected to have the largest bond angle?

Accepted Answer

$$\mathrm{$$BeF_2$$}$$

Question 16

A chemist is analyzing the structure of $$\mathrm{$$ClO_4$$^-}. $$What is the electron group geometry and molecular geometry of this ion?

Accepted Answer

Electron group geometry: tetrahedral; molecular geometry: tetrahedral

Question 17

Which of the following molecules or ions is expected to be polar due to its molecular geometry?

Accepted Answer

$$\mathrm{SO_2$}$$

Question 18

Which of the following is an exception to the octet rule due to having an odd number of electrons?

Accepted Answer

$$\mathrm{NO}$$

Question 19

A molecule has the formula $$\mathrm{$$XeF_2$$}. $$What is its AXE notation and molecular geometry?

Accepted Answer

AX2E3, linear

Question 20

Which of the following best explains why the bond angle in $$\mathrm{NH_3$} is $$less than $$109.5^\circ$$?

Accepted Answer

The lone pair on nitrogen repels the bonding pairs more strongly, compressing the bond angle.

Lewis Structures and Molecular Shapes: Study Guide

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