Question

(a) Draw the Lewis structures for at least four species that have the general formula $$ [: X=Y:]^{n} $$ where \(\mathrm{X}\) and \(\mathrm{Y}\) may be the same or different, and \(n\) may have a value from +1 to -2 . (b) Which of the compounds is likely to be the strongest Bronsted base? Explain. [Sections \(22.1,22.7,\) and 22.9\(]\)

Short answer

The Lewis structures for the four species CO, NO^{-}, SO^{+}, and NN are as follows: CO: :C::[::]O: , NO^{-}: :N::[::]O^- , SO^{+}: [:S:]^+::O: , and NN: :N::[::]N:. Among these species, NO^{-} is likely to be the strongest Bronsted base due to its -1 charge and the electronegativity of the oxygen atom.

Step-by-step solution

Understanding the general formula of the compounds

The general formula given is [: X=Y:]^{n}, where X and Y can be the same or different, and they are both non-metal atoms as they are making a double bond with each other. We also need to remember that n can have a value from +1 to -2. This will give us variations in the compounds.

Choose different combinations of X and Y atoms and determine n for each

Let's choose some combinations of elements for X and Y and determine n for each: (i) CO: X=Carbon (C), Y=Oxygen (O). n=0 (neutral molecule) (ii) NO^{-}: X=Nitrogen (N), Y=Oxygen (O). n=-1 (iii) SO^{+}: X=Sulfur (S), Y=Oxygen (O). n=+1 (iv) NN: X=Nitrogen (N), Y=Nitrogen (N). n=0 (neutral molecule) Now, let's draw their Lewis structures.

Draw the Lewis structures for each compound

(i) CO (Carbon Monoxide): C being the central atom has 4 valence electrons, and O has 6 valence electrons: :C::[::]O: (ii) NO^{-} (Nitrogen Monoxide Ion): N has 5 valence electrons and O has 6 valence electrons, with an added electron because it has a -1 charge.: :N::[::]O^- (iii) SO^{+} (Sulfur-Oxygen Ion): S has 6 valence electrons, and O has 6 valence electrons, with one less electron due to the +1 charge: [:S:]^+::O: (iv) NN (Nitrogen Gas): N has 5 valence electrons: :N::[::]N:

Determine the strongest Bronsted base

Since a Bronsted base is a compound that donates electrons to an H^+ ion, we can assess the strength of a Bronsted base by considering its basicity (or tendency to attract H^+ ions). Several factors can contribute to the basicity of a compound, such as electronegativity and charge. Generally, the more negative the compound, the stronger Bronsted base it is. Based on electronegativity and charge, NO^{-} has a -1 charge, and the oxygen atom is electronegative. Thus, among these species, NO^{-} is likely to be the strongest Bronsted base.

Key concepts

Bronsted Base

The concept of a Bronsted base is central to understanding many chemical reactions, particularly acid-base reactions. According to Bronsted's theory, a base is any substance that can accept a proton (a hydrogen ion, H⁺). This is an important concept to grasp because it helps explain how chemical species interact with each other in a solution.

Analyzing the exercise, we know that the strongest Bronsted base is the one that is most likely to accept a proton. Factors influencing a molecule's ability to act as a base include its charge and the presence of electronegative atoms, such as oxygen, which are keen on attracting protons due to their partial negative charge. Among the listed species, NO^- stands out as the strongest Bronsted base because it has a negative charge, making it more likely to attract and accept a hydrogen ion.

Chemical Bonding

Chemical bonding is the force that holds atoms together in molecules and compounds. At the heart of chemical bonding is the concept of sharing or transferring electrons. There are several types of bonds, but the one we are concerned with here is the covalent bond, where atoms share pairs of valence electrons.

In Lewis structures, which reveal the nature of chemical bonding in molecules, a single line represents a shared pair of electrons, or a single bond. In the molecules from the exercise, like CO or NN, double lines between atoms indicate double bonds, where two pairs of electrons are shared. Determining how these electrons are shared is crucial for predicting molecular properties, reactivity, and how a molecule will interact with others, such as how it behaves as a Bronsted base.

Valence Electrons

The concept of valence electrons is fundamental in understanding chemical bonding and reactivity. These are the electrons that reside in the outermost shell of an atom and participate in the formation of chemical bonds. The number of valence electrons determines an atom's bonding behavior.

For example, in the step-by-step solution provided, carbon in CO has four valence electrons, which it uses to form multiple bonds with oxygen. Similarly, the negative charge in NO^- indicates an extra valence electron that influences its ability to act as a Bronsted base. Recognizing the role valence electrons play is essential for drawing accurate Lewis structures and predicting the properties of a molecule or ion.