Question

Supply a systematic name for each of the following oxyanions: (a) \(\mathrm{CO}_{3}^{2-}\) (b) \(\mathrm{HCO}_{3}^{-}\) (c) \(\mathrm{SO}_{4}{ }^{2-}\) (d) \(\mathrm{HSO}_{4}\)

Short answer

(a) Carbonate, (b) Hydrogen carbonate/Bicarbonate, (c) Sulfate, (d) Hydrogen sulfate/Bisulfate.

Step-by-step solution

Identifying Oxyanions and Base Names

We start by identifying the common oxyanions for each formula. For (a) \( \mathrm{CO}_{3}^{2-} \) and (b) \( \mathrm{HCO}_{3}^{-} \), the base oxyanion is carbonate \( \mathrm{CO}_{3}^{2-} \). Similarly, for (c) \( \mathrm{SO}_{4}^{2-} \) and (d) \( \mathrm{HSO}_{4}^{-} \), the base oxyanion is sulfate \( \mathrm{SO}_{4}^{2-} \). Base names for these oxyanions are 'carbonate' and 'sulfate' respectively.

Naming the Standard Oxyanions

For standard oxyanions consisting of only the nonmetal and oxygen, use the names ending in '-ate'. Therefore, \( \mathrm{CO}_{3}^{2-} \) is named 'carbonate' and \( \mathrm{SO}_{4}^{2-} \) is named 'sulfate'. These are the common names used when the oxyanion doesn’t have any additional hydrogen ions attached.

Naming Hydrogen Combined Oxyanions

When a hydrogen ion is added to an oxyanion, add 'hydrogen' or sometimes '-bi' before the standard oxyanion name. Thus, \( \mathrm{HCO}_{3}^{-} \) is called 'hydrogen carbonate' or 'bicarbonate', and \( \mathrm{HSO}_{4}^{-} \) is called 'hydrogen sulfate' or 'bisulfate'.

Key concepts

Oxyanions

An oxyanion is a type of polyatomic ion that consists of an element, usually a non-metal, bonded to one or more oxygen atoms. These ions carry a negative charge due to the extra electrons required to balance out the charge from the included oxygen atoms. Understanding oxyanions is crucial because they form the basis of many compounds found in nature and are commonly seen in various chemical reactions.
Oxyanions typically end with the suffix '-ate', with a few exceptions. They can vary in their number of oxygen atoms, which occasionally leads to different naming conventions based on oxygen content. Some common examples of oxyanions include:

• Carbonate ( CO_3^{2-})
• Sulfate ( SO_4^{2-})
• Nitrate ( NO_3^{-})
• Phosphate ( PO_4^{3-})

Recognizing these ions and understanding their structure helps in predicting their behavior in chemical reactions.

Carbonate

The carbonate ion, represented as CO_3^{2-} in chemical notation, is one of the fundamental oxyanions encountered in chemistry. It consists of one carbon atom covalently bonded to three oxygen atoms, forming a planar triangle. This structure leads to its significant role in various geological and biological processes.
In the systematic naming of oxyanions, '-ate' denotes the standard structure with a typical number of oxygen atoms. Oxyanions that form salts often derive from carboxylic acids; however, carbonate is unique as it is the salt form of carbonic acid without directly corresponding to a true acid. Common compounds containing carbonate include:

• Calcium carbonate, CaCO_3, found in rocks and shells
• Sodium carbonate, Na_2CO_3, used in glass making and detergents

Understanding carbonates is essential for grasping sedimentary rock formation, ocean chemistry, and even daily industrial processes.

Sulfate

Sulfate, expressed as SO_4^{2-}, plays a pivotal role in many biological and environmental systems. The sulfate ion is composed of one sulfur atom surrounded by four oxygen atoms, where two of the oxygen atoms are bonded to sulfur through double bonds, contributing to the ion's tetrahedral shape.
Sulfate is commonly found in minerals and is a crucial part of the sulfur cycle. It is the oxidized form of sulfur found in various organic compounds and naturally occurring minerals. Here are some examples where sulfate is present:

• Gypsum (CaSO_4 3 H_2O) used in drywall
• Epsom salts (MgSO_4 3 H_2O) used as a laxative and muscle relaxant
• Sulfuric acid (H_2SO_4), a major industrial chemical

Understanding sulfates and their derivatives is critical for students as they explore fields like geology, biology, and industrial chemistry.

Hydrogen Oxyanions

Hydrogen oxyanions such as HCO_3^{-} (hydrogen carbonate or bicarbonate) and HSO_4^{-} (hydrogen sulfate or bisulfate) represent a group of compounds where a hydrogen ion is added to a base oxyanion. These ions typically carry one less negative charge than their non-hydrogenated counterparts, as the hydrogen ion reduces the overall negative charge due to its positive nature.
The addition of the hydrogen in the systematic name indicates the presence of the extra hydrogen atom. Such oxyanions are crucial in various chemical processes, including buffering solutions, where they help maintain pH stability. Examples include:

• Bicarbonate in blood, maintaining pH balance
• Bisulfate in cleaning products
• Bicarbonate used in baking, known as baking soda

Grasping the concept of hydrogen oxyanions paves the way for understanding more intricate reactions and essential everyday applications, like metabolism and cleaning processes.