Problem 86 - Chemistry An Atoms First Approach

Question

What do each of the following sets of compounds/ions have in common with each other? a. \(\mathrm{SO}_{3}, \mathrm{NO}_{3}^{-}, \mathrm{CO}_{3}^{2-}\) b. \(\mathrm{O}_{3}, \mathrm{SO}_{2}, \mathrm{NO}_{2}^{-}\)

Step-by-Step Solution

Answer

The common properties of the given sets of compounds/ions are: Set a (\(\mathrm{SO}_{3}, \mathrm{NO}_{3}^{-}, \mathrm{CO}_{3}^{2-}\)): Total number of 24 valence electrons and trigonal planar molecular geometry. Set b (\(\mathrm{O}_{3}, \mathrm{SO}_{2}, \mathrm{NO}_{2}^{-}\)): Total number of 18 valence electrons and bent molecular geometry.

Step 1: Identify and list the properties of each compound/ion in set a.

For set a with compounds/ions: \(\mathrm{SO}_{3}, \mathrm{NO}_{3}^{-}, \mathrm{CO}_{3}^{2-}\) Property of \(\mathrm{SO}_{3}\): - Contains sulfur and oxygen - Has a total number of 24 valence electrons - Has a trigonal planar molecular geometry Property of \(\mathrm{NO}_{3}^{-}\): - Contains nitrogen and oxygen - Has a total number of 24 valence electrons - Has a trigonal planar molecular geometry - Has a -1 charge Property of \(\mathrm{CO}_{3}^{2-}\): - Contains carbon and oxygen - Has a total number of 24 valence electrons - Has a trigonal planar molecular geometry - Has a -2 charge

Step 2: Identify the common property in set a

Comparing the properties of the compounds/ions in set a, we find that they all have the following common properties: - Total number of 24 valence electrons - Trigonal planar molecular geometry

Step 3: Identify and list the properties of each compound/ion in set b.

For set b with compounds/ions: \(\mathrm{O}_{3}, \mathrm{SO}_{2}, \mathrm{NO}_{2}^{-}\) Property of \(\mathrm{O}_{3}\): - Contains only oxygen - Has a total number of 18 valence electrons - Has a bent molecular geometry Property of \(\mathrm{SO}_{2}\): - Contains sulfur and oxygen - Has a total number of 18 valence electrons - Has a bent molecular geometry Property of \(\mathrm{NO}_{2}^{-}\): - Contains nitrogen and oxygen - Has a total number of 18 valence electrons - Has a bent molecular geometry - Has a -1 charge

Step 4: Identify the common property in set b

Comparing the properties of the compounds/ions in set b, we find that they all have the following common properties: - Total number of 18 valence electrons - Bent molecular geometry

Step 5: Conclusion

In conclusion, the common properties of the given sets of compounds/ions are: Set a: Total number of 24 valence electrons and trigonal planar molecular geometry Set b: Total number of 18 valence electrons and bent molecular geometry

Key Concepts

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom. They play a pivotal role in chemical bonding, as they are the ones involved in forming chemical bonds with other atoms to create compounds. These peripheral electrons are what determine the chemical properties and reactivity of an element. The number of valence electrons an atom has is related to its position in the periodic table: for main group elements, the group number indicates the number of valence electrons for an atom of that element.

For example, oxygen, found in Group 16 of the periodic table, typically has six valence electrons, while nitrogen, in Group 15, has five. Learning to count valence electrons is fundamental when predicting the chemical bonds that an element can form. In the exercise provided, we saw that the compounds of set a, such as \(\mathrm{SO}_{3}\) and \(\mathrm{NO}_{3}^{-}\), each have a total of 24 valence electrons, highlighting the importance of these electrons in determining the structure and charge of the molecules.

Chemical Compounds

Chemical compounds consist of two or more different elements bonded together in a fixed proportion. The formation of compounds is governed by the octet rule, which states that atoms tend to combine in such a way that they each have eight electrons in their valence shell, giving them the same electronic configuration as a noble gas. The various bonds formed during compound creation include ionic, covalent, and metallic bonds—with covalent being the type of bond that involves the sharing of valence electrons between atoms.

In our exercise, compounds like \(\mathrm{SO}_{2}\) and \(\mathrm{CO}_{3}^{2-}\) are formed through covalent bonding where sulfur or carbon share their valence electrons with oxygen atoms to achieve stable electronic configurations. Understanding the composition of compounds and the types of chemical bonds involved is crucial for grasping the concept of molecular geometry which is influenced by how atoms bond within a molecule.

Molecular Geometry

Molecular geometry, or molecular shape, refers to the three-dimensional arrangement of atoms within a molecule. This geometric structure greatly influences the physical and chemical properties of the molecule, such as boiling point, polarity, and reactivity. VSEPR theory (Valence Shell Electron Pair Repulsion) is commonly used to predict the geometry of molecules based on the repulsion between electron pairs in the valence shell of the central atom.

Considering the compounds from the exercise, \(\mathrm{SO}_{3}\), \(\mathrm{NO}_{3}^{-}\), and \(\mathrm{CO}_{3}^{2-}\) all share a trigonal planar geometry, meaning the atoms are arranged in a flat, three-pointed shape with 120-degree angles between bonds. Conversely, the compounds in set b, including \(\mathrm{O}_{3}\), \(\mathrm{SO}_{2}\), and \(\mathrm{NO}_{2}^{-}\), exhibit a bent molecular geometry. This shape occurs because of the two lone pairs of electrons on the central atom, creating a V-shaped structure. By comparing molecular geometries, students can gain better insight into the behavior and interaction of different chemical compounds.