Question

Is O2 always a double bond?

Answer 1

BRINCLHOF

Br

I

N

Cl

H

O

F

all have dounle bonds.

You could also do lewis structures for each molecule to figure out the structure.

Answer 2

• O-O single bonds and H-O single bonds in $\text{H}_2\text{O}_2$ molecules.
• H-O single bonds in $\text{H}_2\text{O}$ molecules.
• O=O double bonds in $\text{O}_2$ molecules.

Explanation

How many valence electrons do atoms in each molecule need for them to be stable?

• Each H atom needs two valence electrons to be stable.
• Each atom of an element other than H needs eight valence electron to be stable.

• There are two H atoms and two O atoms in an  $\text{H}_2\text{O}_2$ molecule. Atoms in each $\text{H}_2\text{O}_2$ need $2 \times 1 + 2\times 2 = 6$ more electrons to be stable.
• There are two H atoms and one O atom in an $\text{H}_2\text{O}$ molecule. Atoms in each $\text{H}_2\text{O}$ molecule need $2 \times 1 + 2= 4$ more electrons to be stable.
• There are two O atoms in an $\text{O}_2$ molecule. Atoms in each $\text{O}_2$ molecule need $2 \times 2 = 4$ more electrons to be stable.

How many chemical bonds in each molecule?

Each chemical bond adds one valence electron to each bonding atom. Each chemical bond connects two atoms. As a result, each chemical bond adds two valence electrons to the molecule.

• Each $\text{H}_2\text{O}_2$ molecule needs $6 / 2 = 3$ chemical bonds.
• Each $\text{H}_2\text{O}$ molecule needs $4 / 2 = 2$ chemical bonds.
• Each $\text{O}_2$ molecule needs $4 /2= 2$ chemical bonds.

What chemical bonds are these? Again, each H atom needs only one more valence electron to be stable. It will share only one electron with O and form one H-O bond. The rest of the chemical bonds are between O atoms.

• There are two H atoms in each $\text{H}_2\text{O}_2$ molecule, which form two H-O bonds. Two of the three chemical bonds in this molecule are H-O. The other is an O-O single bond between the two O atoms.
• There are two H atoms in each $\text{H}_2\text{O}$ molecule, which form two H-O bonds. Both chemical bonds in this molecule are H-O. There's no O-O bond in this molecule.
• There is no H atom in $\text{O}_2$ molecules. Both chemical bonds are between O atoms. However, there are only two O atoms. There must be two chemical bonds between the two O atoms. That bond will be an O-O double bond.