$\text{Sum of valence electrons of all atoms} + 2$

Question 1

Which of the following molecules violates the octet rule by having more than eight electrons around its central atom?

Accepted Answer

SF$_6$

Question 2

How many valence electrons are present in the Lewis structure of the hydronium ion, H$_3$O$^+$?

Accepted Answer

$8$

Question 3

When drawing the Lewis structure for CN$^-$, how many total valence electrons must be used?

Accepted Answer

$10$

Question 4

Which of the following statements about resonance structures is TRUE?

Accepted Answer

Only electrons are moved, not atoms, when drawing resonance structures.

Question 5

What is the molecular geometry and bond angle of a molecule with three electron groups and one lone pair around the central atom?

Accepted Answer

Bent, $120^	ext{o}$

Question 6

Which of the following molecules has a trigonal pyramidal molecular shape?

Accepted Answer

NH$_3$

Question 7

A molecule of H$_2$S has two lone pairs and two bonded atoms around the central atom. What is its electron-group geometry and molecular shape?

Accepted Answer

Tetrahedral, bent

Question 8

How many electrons are shared in a triple bond?

Accepted Answer

$6$

Question 9

Which of the following is a correct Lewis structure for the cyanide ion, CN$^-$?

Accepted Answer

$[:N\equiv C:]^{-}$

Question 10

Which of the following elements is LEAST likely to form double or triple bonds?

Accepted Answer

Hydrogen

Question 11

What is the total number of valence electrons in a molecule of C$_2$H$_4$?

Accepted Answer

$12$

Question 12

Which of the following is TRUE about the octet rule exceptions?

Accepted Answer

Elements in period 3 or higher can have more than eight electrons.

Question 13

A molecule has four electron groups around its central atom, with two lone pairs. What is its molecular shape and approximate bond angle?

Accepted Answer

Bent, $109^	ext{o}$

Question 14

Which of the following best describes the difference between electron-group geometry and molecular shape?

Accepted Answer

Electron-group geometry considers both atoms and lone pairs, while molecular shape considers only atoms.

Question 15

In the Lewis structure for NO$_2^-$, resonance structures are possible. What does this mean for the actual molecule?

Accepted Answer

The molecule exists as an average (hybrid) of all resonance structures.

Question 16

Which of the following is the correct formula for calculating the total number of valence electrons in a polyatomic ion with a $-2$ charge?

Accepted Answer

$	ext{Sum of valence electrons of all atoms} + 2$

Question 17

Which molecule has a linear molecular geometry?

Accepted Answer

CO$_2$

Question 18

A molecule has three electron groups around its central atom: two atoms and one lone pair. What is its molecular shape?

Accepted Answer

Bent

Question 19

Which of the following is TRUE about the sharing of electrons in bonds?

Accepted Answer

A single bond shares two electrons.

Question 20

Which of the following is the correct Lewis structure for the hydronium ion, H$_3$O$^+$?

Accepted Answer

$[\mathrm{H}\underset{..}{\mathrm{O}}-\mathrm{H}-\mathrm{H}]^{+}$

Lewis Structures, the Octet Rule, and Molecular Geometry

Study Guide - Practice Questions