Question

Give the name of each of the following polyatomic ions. a. \(\mathrm{HCO}_{3}^{-}\) b. \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\) c. \(\mathrm{CN}^{-}\) d. \(\mathrm{OH}^{-}\) e. \(\mathrm{NO}_{2}^{-}\) f. \(\mathrm{HPO}_{4}^{2-}\)

Short answer

a. Bicarbonate or Hydrogen carbonate b. Acetate c. Cyanide d. Hydroxide e. Nitrite f. Hydrogen phosphate

Step-by-step solution

a. Naming \(\mathrm{HCO}_{3}^{-}\)

The polyatomic ion \(\mathrm{HCO}_{3}^{-}\) is known as bicarbonate ion or hydrogen carbonate ion. The name "bicarbonate" comes from the presence of one hydrogen ion (H) and one carbonate ion (CO3) in this ion.

b. Naming \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\)

The polyatomic ion \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\) is known as acetate ion. The name "acetate" comes from the presence of two carbons (C2), three hydrogens (H3), and two oxygen atoms (O2) in this ion.

c. Naming \(\mathrm{CN}^{-}\)

The polyatomic ion \(\mathrm{CN}^{-}\) is called the cyanide ion. The name "cyanide" comes from the presence of one carbon atom (C) and one nitrogen atom (N) in this ion.

d. Naming \(\mathrm{OH}^{-}\)

The polyatomic ion \(\mathrm{OH}^{-}\) is known as hydroxide ion. The name "hydroxide" comes from the presence of one hydrogen atom (H) and one oxygen atom (O) in this ion.

e. Naming \(\mathrm{NO}_{2}^{-}\)

The polyatomic ion \(\mathrm{NO}_{2}^{-}\) is called the nitrite ion. The name "nitrite" comes from the presence of one nitrogen atom (N) and two oxygen atoms (O2) in this ion. Note that this is different from nitrate ion (NO3-) which has three oxygen atoms.

f. Naming \(\mathrm{HPO}_{4}^{2-}\)

The polyatomic ion \(\mathrm{HPO}_{4}^{2-}\) is known as hydrogen phosphate ion. The name "hydrogen phosphate" comes from the presence of one hydrogen ion (H), one phosphorus atom (P), and four oxygen atoms (O4) in this ion.

Key concepts

Chemical Nomenclature

Chemical nomenclature is all about naming chemical compounds. It helps scientists communicate clearly about chemical substances. Names are derived based on rules set by organizations like IUPAC (International Union of Pure and Applied Chemistry).

For polyatomic ions, these names usually reflect the composition of the ion. For example, the ion \( \mathrm{OH}^{-} \) is named "hydroxide," indicating its hydrogen and oxygen content. Learning how names relate to structures can help you identify compounds more easily.

• Prefixes and Suffixes: These help distinguish ions with different oxygen levels. For example, "-ite" (nitrite, \( \mathrm{NO}_{2}^{-} \)) often has fewer oxygen atoms than "-ate" (nitrate, \( \mathrm{NO}_{3}^{-} \)).
• Presence of Hydrogen: Ions like bicarbonate \( \mathrm{HCO}_{3}^{-} \) indicate hydrogen by using prefixes like "hydrogen."

Understanding these naming conventions is key to mastering chemical nomenclature.

Inorganic Chemistry

Inorganic chemistry focuses on compounds that are not primarily based on carbon, excluding most organic compounds. It covers a wide range of substances, including metals, minerals, and organometallic compounds.

Polyatomic ions are a major part of inorganic chemistry. They consist of multiple atoms bonded together, behaving as a single charged entity. Examples include acetate \( \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-} \) and cyanide \( \mathrm{CN}^{-} \).

• Complex Structures: These ions can have intricate structures, such as phosphate \( \mathrm{HPO}_{4}^{2-} \).
• Importance in Reactions: They play crucial roles in various chemical reactions, such as neutralizing acids.

Grasping the fundamentals of inorganic chemistry can deepen your understanding of chemical reactivity and bonding.

Anion Identification

Anions are negatively charged ions, formed when an atom or molecule gains electrons. Identifying them involves recognizing specific charge and composition patterns.

Polyatomic anions, like those mentioned earlier, have unique compositions and charges. For instance, hydrogen phosphate \( \mathrm{HPO}_{4}^{2-} \) carries a 2- charge due to extra electrons added to the molecule.

• Charge Recognition: Understanding the charge helps predict how anions interact in chemical reactions.
• Common Patterns: Familiar patterns, like the "-ate" and "-ite" suffixes, assist in distinguishing various anions.

Learning these patterns aids in the accurate identification and usage of anions in both practical and theoretical chemistry.