Question 1

Why does hydroxide have a negative charge?

Accepted Answer

OH- has one more valence electron than neutral OH. That extra electron remains on oxygen, giving oxygen three lone pairs and a formal charge of -1.

Question 2

Why does CO₂ have double bonds instead of single bonds?

Accepted Answer

Two single bonds leave carbon with only four electrons. One lone pair from each oxygen is shared with carbon, creating two C=O double bonds so carbon and both oxygens complete their octets with zero formal charge.

Question 3

How many lone pairs does oxygen have in H₂O?

Accepted Answer

The oxygen atom in H₂O has two lone pairs. The other four valence electrons form the two O–H single bonds.

Question 4

What shapes do CO₂ and H₂O have?

Accepted Answer

CO₂ is linear because its central carbon has two bonding domains and no lone pairs. H₂O is bent because its central oxygen has two bonding pairs and two lone pairs.

Question 5

How many valence electrons are in the neutral OH molecule?

Accepted Answer

Neutral OH has 7 valence electrons: 6 from oxygen and 1 from hydrogen. Because the total is odd, one electron remains unpaired on oxygen, so OH is a radical.

Question 6

What is the Lewis structure of the neutral hydroxyl radical?

Accepted Answer

Neutral OH has one O–H single bond, two lone pairs on oxygen, and one unpaired electron on oxygen. Both hydrogen and oxygen have formal charge 0.

Question 7

How does the Lewis structure of OH⁻ differ from neutral OH?

Accepted Answer

OH⁻ has one extra electron compared with neutral OH. The extra electron pairs with the unpaired electron, giving oxygen three lone pairs and a complete octet.

Question 8

Why is OH⁻ written inside brackets in a Lewis structure?

Accepted Answer

The brackets show that the displayed atoms and electrons belong to a polyatomic ion. The superscript − outside the brackets indicates the ion's overall charge.

Question 9

What are the formal charges in the usual Lewis structure of OH⁻?

Accepted Answer

Hydrogen has a formal charge of 0 and oxygen has a formal charge of −1. These formal charges add to the overall −1 charge of hydroxide.

Question 10

Why is CO₂ drawn with two C=O double bonds?

Accepted Answer

Two C=O double bonds give carbon and both oxygen atoms complete octets while keeping all formal charges at 0. The resulting structure is O=C=O.

Question 11

What is the usual Lewis structure and formal-charge pattern of CO?

Accepted Answer

The usual structure is ⁻C≡O⁺. The triple bond and one lone pair on each atom give both atoms complete octets, with −1 on carbon and +1 on oxygen.

Question 12

Why does H₂O have two lone pairs on oxygen?

Accepted Answer

Water has 8 valence electrons. Four form the two O–H bonds, and the remaining four electrons stay on oxygen as two lone pairs.

Question 13

How do lone pairs affect the shape of H₂O?

Accepted Answer

The two lone pairs on oxygen repel the O–H bonding pairs, making H₂O bent rather than linear. Its bond angle is approximately 104.5°.

Question 14

Which molecule or ion in the explorer has an unpaired electron?

Accepted Answer

Only neutral OH has an unpaired electron. OH⁻ has one additional electron that pairs with it, while CO₂, CO, and H₂O are shown with paired electrons in their usual Lewis structures.

Question 15

Why does ozone have two Lewis resonance structures?

Accepted Answer

The O=O double bond can be drawn to either side of the central oxygen. These two equivalent resonance structures have the same arrangement of atoms, but the positions of the double bond and negative formal charge are exchanged.

Question 16

What are the formal charges in the usual Lewis structure of ozone?

Accepted Answer

In either major resonance form, the central oxygen has a formal charge of +1, the singly bonded terminal oxygen has −1, and the double-bonded terminal oxygen has 0. The charges sum to zero because ozone is neutral.

Question 17

How many valence electrons are in the carbonate ion, CO₃²⁻?

Accepted Answer

Carbonate has 24 valence electrons: 4 from carbon, 18 from the three oxygen atoms, and 2 additional electrons from the 2− charge.

Question 18

Why does carbonate have three equivalent resonance structures?

Accepted Answer

The C=O double bond can be placed between carbon and any one of the three oxygen atoms. Moving the double bond gives three equivalent resonance contributors with the same overall 2− charge.

Question 19

What are the formal charges in a carbonate resonance structure?

Accepted Answer

The central carbon has a formal charge of +1, the double-bonded oxygen has 0, and each singly bonded oxygen has −1. These charges add to the overall 2− charge of CO₃²⁻.

Question 20

What is the shape of the carbonate ion?

Accepted Answer

Carbonate is trigonal planar. The central carbon has three bonding regions and no lone pairs, so the O–C–O bond angles are approximately 120°.

Question 21

How many valence electrons are in CCl₄?

Accepted Answer

CCl₄ has 32 valence electrons: 4 from carbon and 7 from each of the four chlorine atoms.

Question 22

How many lone pairs are present in the Lewis structure of CCl₄?

Accepted Answer

Each chlorine atom has three lone pairs, so CCl₄ has twelve lone pairs in total. The central carbon has no lone pairs.

Question 23

What is the shape of CCl₄ and its approximate bond angle?

Accepted Answer

CCl₄ is tetrahedral because four bonding pairs surround the central carbon and there are no lone pairs on it. The Cl–C–Cl bond angles are approximately 109.5°.

Question 24

How many valence electrons are in NH₃?

Accepted Answer

Ammonia has 8 valence electrons: 5 from nitrogen and 1 from each of the three hydrogen atoms.

Question 25

How many lone pairs are present on nitrogen in NH₃?

Accepted Answer

Nitrogen has one lone pair in NH₃. The other six valence electrons form the three N–H single bonds.

Question 26

Why is NH₃ trigonal pyramidal instead of planar?

Accepted Answer

The central nitrogen has three bonding pairs and one lone pair. Repulsion from the lone pair pushes the N–H bonds downward, giving NH₃ a trigonal-pyramidal shape with an angle of about 107°.

Question 27

How many valence electrons are in NH₄⁺?

Accepted Answer

NH₄⁺ has 8 valence electrons: 5 from nitrogen, 4 from the hydrogen atoms, minus 1 because of the positive charge.

Question 28

Why does NH₄⁺ have no lone pair on nitrogen?

Accepted Answer

The four N–H single bonds use all 8 valence electrons in NH₄⁺. The positive charge results from removing the lone-pair electron from NH₃ when the proton bonds to nitrogen.

Question 29

What is the shape of NH₄⁺?

Accepted Answer

NH₄⁺ is tetrahedral. Nitrogen has four bonding regions and no lone pairs, with H–N–H angles of approximately 109.5°.

Lewis Dot Structure

Carbon dioxide · CO₂

About Lewis Dot Structure

Lewis Dot Structure

Carbon dioxide · CO₂

About Lewis Dot Structure

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