Q: Which of the following is the correct formula for calculating formal charge?

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

Question 1

Which of the following statements about Lewis structures is TRUE?

Accepted Answer

Each line in a Lewis structure represents a pair of shared electrons (a covalent bond).

Question 2

How many valence electrons are present in a molecule of CH$$_3NH$_2$$?

Accepted Answer

$$14$$

Question 3

Which atom is most likely to be the central atom in a Lewis structure for the molecule CH$$_3CH$_2OH$$?

Accepted Answer

Carbon

Question 4

What is the formal charge on the oxygen atom in the hydroxide ion (OH$$^-$$)?

Accepted Answer

$$-1$$

Question 5

Which of the following best describes the difference between bonding and nonbonding electrons in Lewis structures?

Accepted Answer

Bonding electrons are shared between atoms, nonbonding electrons are lone pairs on a single atom.

Question 6

A student draws the Lewis structure for NaCl. Which of the following is the correct representation?

Accepted Answer

$$\mathrm{Na}^{+} \quad [\mathrm{Cl}^{-}]$$ with Cl surrounded by 8 dots

Question 7

How many total valence electrons are present in a molecule of Br$$_2$$?

Accepted Answer

$$14$$

Question 8

Which of the following steps is NOT part of the standard procedure for drawing a Lewis structure?

Accepted Answer

Assign all electrons as lone pairs before forming any bonds.

Question 9

What is the formal charge on nitrogen in the nitrate ion (NO$$_3^-$$)?

Accepted Answer

$$0$$

Question 10

In the Lewis structure for CH$$_3$$COOH (acetic acid), how many lone pairs are present on the oxygen atoms?

Accepted Answer

$$4$$

Question 11

Which of the following molecules contains a double bond in its Lewis structure?

Accepted Answer

CO$$_2$$

Question 12

A student is asked to draw the Lewis structure for NO$$_2^-. $$What is the total number of valence electrons to be used?

Accepted Answer

$$18$$

Question 13

Which of the following is a correct statement about the octet rule?

Accepted Answer

Hydrogen is an exception to the octet rule and only needs two electrons.

Question 14

What is the formal charge on the chlorine atom in Cl$$^-$$?

Accepted Answer

$$-1$$

Question 15

Which of the following best explains why Na$$^+$$ and Cl$$^-$$ form an ionic compound?

Accepted Answer

Na$$^+$$ and Cl$$^-$$ are attracted by electrostatic forces due to opposite charges.

Question 16

In the Lewis structure for water (H$$_2O$$), how many lone pairs are present on the oxygen atom?

Accepted Answer

$$2$$

Question 17

Which of the following molecules has a central atom with fewer than eight electrons in its Lewis structure?

Accepted Answer

BF$$_3$$

Question 18

A student draws the Lewis structure for CH$$_4. $$How many bonding pairs and lone pairs are present?

Accepted Answer

4 bonding pairs, 0 lone pairs

Question 19

Which of the following is the correct formula for calculating formal charge?

Accepted Answer

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

Question 20

Which of the following molecules would you expect to have resonance structures?

Accepted Answer

NO$$_2^-$$

Particle Drawing and Lewis Structures in General Chemistry

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