Question

The hypochlorite ion, \(\mathrm{ClO}^{-},\) is the active ingredient in bleach. The perchlorate ion, \(\mathrm{ClO}_{4}^{-},\) is a main component of rocket propellants. Draw Lewis structures for both ions.

Short answer

The Lewis structure for the hypochlorite ion (ClO-) is: O || Cl- The Lewis structure for the perchlorate ion (ClO4-) is: O || O--Cl--O- || O

Step-by-step solution

Count the number of valence electrons

For both ClO- and ClO4-, we need to count the valence electrons of each atom and add an extra electron for the negative charge. Chlorine (Cl) has 7 valence electrons and Oxygen (O) has 6. For ClO-: Total valence electrons = 7 (from Cl) + 6 (from O) + 1 (negative charge) = 14 For ClO4-: Total valence electrons = 7 (from Cl) + 4*6 (from 4 O atoms) + 1 (negative charge) = 32

Arrange the atoms and distribute the electrons (ClO-)

First, we look at ClO-. Chlorine will be the central atom, and oxygen will be bonded to it. We will start by creating a single bond between chlorine and oxygen, which uses 2 electrons (1 pair). Then, distribute the remaining electrons to satisfy the octet rule for each atom: • Chlorine needs 6 more electrons or 3 lone pairs (total: 6 + 1*2 = 8). • Oxygen needs 6 more electrons or 3 lone pairs (total: 6 + 1*2 = 8). Now we have used all 14 valence electrons, and both atoms satisfy the octet rule.

Drawing the Lewis structure (ClO-)

The Lewis structure for the hypochlorite ion (ClO-) will look like this: O || Cl- Here, the central chlorine atom (Cl) has one single bond to the oxygen atom (O), and each atom has 3 lone pairs of electrons. The negative charge is assigned to the chlorine atom.

Arrange the atoms and distribute the electrons (ClO4-)

Now, we look at ClO4-. Chlorine will be the central atom, with the 4 oxygen atoms bonded around it. We will start by creating single bonds between chlorine and each of the 4 oxygen atoms, which uses 8 electrons (4 pairs). Then, distribute the remaining electrons to satisfy the octet rule for each atom: • Chlorine needs 4 more electrons or 2 lone pairs (total: 4 + 4*2 = 8). • Each oxygen needs 6 more electrons or 3 lone pairs (total: 6 + 1*2 = 8). Now we have used all 32 valence electrons, and all atoms satisfy the octet rule.

Drawing the Lewis structure (ClO4-)

The Lewis structure for the perchlorate ion (ClO4-) will look like this: O || O--Cl--O- || O Here, the central chlorine atom (Cl) has single bonds to each of the 4 oxygen atoms; each oxygen atom has 3 lone pairs of electrons. The negative charge is assigned to one of the oxygen atoms. These are the Lewis structures for hypochlorite ion (ClO-) and perchlorate ion (ClO4-).

Key concepts

Valence Electrons

Understanding valence electrons is crucial when drawing Lewis Structures. Valence electrons are the electrons that reside in the outermost shell of an atom. These are the electrons involved in chemical bonding. For instance, in the hypochlorite ion \(\text{ClO}^{-}\), chlorine (Cl) has 7 valence electrons, and oxygen (O) has 6. The negative charge adds an extra electron, leading to a total of 14 valence electrons.

• Chlorine: 7 valence electrons
• Oxygen: 6 valence electrons
• Extra due to negative charge: 1

For the perchlorate ion \(\text{ClO}_4^{-}\), we follow a similar principle, but remember to multiply the oxygen's valence electrons by four as there are four oxygen atoms bonded:

• Chlorine: 7 valence electrons
• Oxygen: 4×6 = 24 valence electrons
• Extra due to negative charge: 1

This results in a total of 32 valence electrons for \(\text{ClO}_4^{-}\). Getting the valence electrons count right ensures that the electron configuration will satisfy chemical bonding rules.

Octet Rule

The octet rule is a guiding principle in drawing Lewis structures, which states that atoms tend to form bonds until they are surrounded by eight valence electrons. This rule applies to most atoms, though smaller atoms like hydrogen follow the "duet rule" with two electrons.
In \(\text{ClO}^{-}\), chlorine and oxygen aim to achieve octets:- **Chlorine and Oxygen**: Start with a single bond using two electrons, then assign lone pairs. Chlorine and oxygen each receive six more electrons or three lone pairs, reaching an octet of 8 electrons.In \(\text{ClO}_4^{-}\), each oxygen atom forms a single bond with chlorine:- **Chlorine and Oxygen**: Each oxygen bonds with chlorine using two electrons, satisfying the octet for chlorine by using an additional two lone pairs (6 electrons). Each oxygen is surrounded by three lone pairs besides the bond, making an octet.Remember, the extra electrons are distributed to atoms in need, maintaining stability.

Hypochlorite Ion

The hypochlorite ion \(\text{ClO}^{-}\) is the active component in many cleaning solutions. When drawing its Lewis structure, we place chlorine as the central atom because it can more easily accommodate additional electrons compared to oxygen. Following the rules:1. **Single Bond Formation**: Form a single bond between chlorine and oxygen that uses 2 electrons.2. **Distribute Remaining Electrons**: Allocate the remaining 12 electrons as lone pairs around both atoms to satisfy their octets.3. **Resulting Structure**: - Chlorine: 3 lone pairs and 1 bond pair (total 8 electrons) - Oxygen: 3 lone pairs and 1 bond pair (total 8 electrons)These bonds and arrangements ensure the hypochlorite ion is stable and matches its chemical roles.

Perchlorate Ion

Perchlorate ion \(\text{ClO}_4^{-}\) is often found in propellant formulations like rocket fuels. Its Lewis structure involves a chlorine atom bonded to four oxygen atoms:1. **Set-Up With Single Bonds**: Chlorine serves as the central atom, exhibiting single bonds with each of the four oxygens. This utilizes 8 electrons.2. **Assigning Electrons**: Assign the remaining 24 valence electrons as lone pairs to complete the octet for every oxygen atom, fulfilling each with 8 electrons. - **Oxygen Atom's Electron Configuration**: 3 lone pairs, 1 shared pair per each oxygen, making the octet complete. - **Chlorine's Octet**: Already satisfied due to the presence of four bond pairs.The extra electron accounting for the ion's negative charge is assigned to one of the oxygen atoms, which is reflective of the molecular stability.