Question

Give the Lewis structure of (a) \(\mathrm{Cl}_{2} \mathrm{O}\) (b) \(\mathrm{N}_{2} \mathrm{O}\) (c) \(\mathrm{P}_{4}\) (d) \(\mathrm{N}_{2}\)

Short answer

Based on the given step-by-step solution, provide the Lewis structures for each molecule: (a) Cl₂O (Dichlorine monoxide) Lewis structure: Cl - O - Cl : : : (b) N₂O (Dinitrogen oxide) Lewis structure: N ≡ O - N (c) P₄ (Tetraphosphorus) Lewis structure: P / \ P - P \_/ P (d) N₂ (Dinitrogen) Lewis structure: N ≡ N

Step-by-step solution

Count valence electrons

First, find the number of valence electrons for each atom in the molecule. For Oxygen, there are 6. For Chlorine, there are 7. Since we have 2 chlorine atoms, the total number of valence electrons is: 6 + 2(7) = 20.

Lewis structure

Place oxygen in the middle with one chlorine atom on each side. Start by connecting each chlorine to the oxygen with a single bond. Each chlorine has 6 additional electrons and oxygen has 4, so we can assign 2 more electrons (lone pairs) to each chlorine and 1 more pair to the oxygen. Cl - O - Cl : : The Lewis structure for \(\mathrm{Cl}_{2} \mathrm{O}\) is completed. (b) \(\mathrm{N}_{2} \mathrm{O}\)

Count valence electrons

First, find the number of valence electrons for each atom in the molecule. For nitrogen, there are 5. For oxygen, there are 6. Total valence electrons: 2(5) + 6 = 16.

Lewis structure

Place the oxygen between the two nitrogen atoms. Connect each nitrogen to oxygen with a single bond. Assign 2 lone pairs to the oxygen and one lone pair to each nitrogen. N - O - N does not yet fulfill the octet rule for the nitrogens. To achieve an octet, create a triple bond between one nitrogen and oxygen and keep the other nitrogen-oxygen bond as a single bond: N \(\equiv\) O - N. The Lewis structure for \(\mathrm{N}_{2} \mathrm{O}\) is completed. (c) \(\mathrm{P}_{4}\)

Count valence electrons

First, find the number of valence electrons for phosphorus. Each phosphorus atom has 5 valence electrons, and there are 4 atoms in the molecule. Total valence electrons: 4(5) = 20.

Lewis structure

Arrange the four phosphorus atoms in a square, and connect each phosphorus atom to two other phosphorus atoms with a single bond, forming a tetrahedron: ``` P / \ P - P \_/ P ``` Each phosphorus atom now has 6 electrons, and by adding 1 lone pair to each phosphorus atom, the octet rule will be satisfied. The Lewis structure for \(\mathrm{P}_{4}\) is completed. (d) \(\mathrm{N}_{2}\)

Count valence electrons

First, find the number of valence electrons for nitrogen. Each nitrogen atom has 5 valence electrons, and there are 2 atoms in the molecule. Total valence electrons: 2(5) = 10.

Lewis structure

Connect the two nitrogen atoms with a single bond. This leaves 3 unpaired electrons on each nitrogen. To fulfill the octet rule, create a triple bond: N \(\equiv\) N. The Lewis structure for \(\mathrm{N}_{2}\) is completed.

Key concepts

Valence Electrons

Valence electrons are the electrons that reside in the outermost shell of an atom and play a pivotal role in chemical reactions. They are the electrons available for bonding with other atoms. For instance, in Oxygen (\textbf{O}), there are 6 valence electrons, while in Chlorine (\textbf{Cl}), there are 7. In the case of the \textbf{Cl}\(_2\)\textbf{O} compound, the total number of valence electrons is calculated by adding together the valence electrons of each atom: 6 for Oxygen and 7 for each Chlorine, resulting in a total of 20 valence electrons.

Counting Valence Electrons

Before drawing a Lewis structure, we count the number of valence electrons of each atom, which is essential for understanding how the atoms will bond. This step is crucial for correctly predicting the structure and behavior of a molecule. Once the total number of valence electrons is known, the distribution of these electrons among atoms in the molecule can begin to satisfy the bonding requirements, commonly guided by the octet rule.

Octet Rule

The octet rule is one of the fundamental principles of chemical bonding. It states that atoms tend to form bonds in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. There are exceptions, but for many elements, adhering to the octet rule results in a more stable, lower energy configuration.

When creating Lewis structures, our goal is to give each atom an octet of electrons. This rule guides us in the placement of electrons around the atoms. For instance, in the Lewis structure for \textbf{N}\(_2\)\textbf{O}, the two Nitrogen (\textbf{N}) atoms and one Oxygen atom must be arranged so that each Nitrogen achieves eight electrons in its shell. We initially connect them with single bonds and then adjust the bonding to ensure that each atom fulfills the octet requirement, as seen with the creation of the triple bond between one Nitrogen atom and Oxygen.

Chemical Bonding

Chemical bonding refers to the forces that hold atoms together within a compound. In the context of Lewis structures, the primary types of bonds we consider are ionic and covalent. Covalent bonds, which are the focus of Lewis structure exercises, involve the sharing of electron pairs between atoms. For example, in the molecule \textbf{N}\(_2\), we start with a single covalent bond and then introduce multiple bonds, specifically a triple bond, to ensure both Nitrogen atoms achieve the octet configuration.

Creating Stronger Bonds

Multiple bonds (double or triple) are a possibility when single bonds don't allow each atom to reach an octet. In the \textbf{P}\(_4\) molecule, each Phosphorus atom starts with two single bonds and achieves an octet by adding lone pairs. In the \textbf{N}\(_2\) molecule, to satisfy the octet rule for both Nitrogen atoms, a triple bond is necessary, as sequential adjustment from single to triple bonds provides the necessary shared electrons.