Question

Many familiar substances have common, unsystematic names. For each of the following, give the correct systematic name: (a) saltpeter, \(\mathrm{KNO}_{3}\); (b) soda ash, \(\mathrm{Na}_{2} \mathrm{CO}_{3}\); (c) lime, \(\mathrm{CaO}\); (d) muriatic acid, \(\mathrm{HCl}\); (e) Epsom salts, \(\mathrm{MgSO}_{4}\); (f) milk of magnesia, \(\mathrm{Mg}(\mathrm{OH})_{2}\)

Short answer

(a) Potassium Nitrate; (b) Sodium Carbonate; (c) Calcium Oxide; (d) Hydrochloric Acid; (e) Magnesium Sulfate; (f) Magnesium Hydroxide

Step-by-step solution

(Step 1: Identify the Ions in Each Formula)

For each chemical formula, identify the cation (positive ion) and the anion (negative ion) present in the substance. (a) KNO\(_3\) : Cation = \(\mathrm{K}^+\) (Potassium ion), Anion = \(\mathrm{NO}_{3}^-\) (Nitrate ion) (b) Na\(_2\)CO\(_3\) : Cation = \(\mathrm{Na}^+\) (Sodium ion), Anion = \(\mathrm{CO}_{3}^{2-}\) (Carbonate ion) (c) CaO : Cation = \(\mathrm{Ca}^{2+}\) (Calcium ion), Anion = \(\mathrm{O}^{2-}\) (Oxide ion) (d) HCl : Cation = \(\mathrm{H}^+\) (Hydrogen ion), Anion = \(\mathrm{Cl}^-\) (Chloride ion) (e) MgSO\(_4\) : Cation = \(\mathrm{Mg}^{2+}\) (Magnesium ion), Anion = \(\mathrm{SO}_{4}^{2-}\) (Sulfate ion) (f) Mg(OH)\(_2\) : Cation = \(\mathrm{Mg}^{2+}\) (Magnesium ion), Anion = \(\mathrm{OH}^-\) (Hydroxide ion)

(Step 2: Write the Systematic Names)

Write the systematic names of each substance by combining the names of the cation and anion. The cation should always come first, followed by the anion. (a) KNO\(_3\) : Potassium Nitrate (b) Na\(_2\)CO\(_3\) : Sodium Carbonate (c) CaO : Calcium Oxide (d) HCl : Hydrochloric Acid (e) MgSO\(_4\) : Magnesium Sulfate (f) Mg(OH)\(_2\) : Magnesium Hydroxide

Key concepts

Systematic Names of Compounds

Understanding the systematic names of compounds is vital in chemistry. It helps students and professionals communicate effectively about chemical substances. Systematic nomenclature follows rules that are universally accepted by the International Union of Pure and Applied Chemistry (IUPAC). This ensures each compound has a unique and descriptive name.

For instance, everyday chemicals like baking soda have common names that are not specific or indicative of their chemical structure. The systematic name for baking soda, NaHCO₃, is sodium bicarbonate, which provides clear information about its ionic components: sodium ions (Na⁺) and bicarbonate ions (HCO₃^-).

Another example is calcium carbonate, commonly referred to as limestone. Its systematic name reveals its constituents, the calcium ion (Ca²⁺) and the carbonate ion (CO₃^2-). Systematic nomenclature bridges the gap between common vernacular and precise chemical language, allowing for an unambiguous understanding of the chemical in question.

Cation and Anion Identification

Identifying the cation and anion components of an ionic compound is a fundamental step in understanding chemical formulas. Cations are positively charged ions, while anions are negatively charged. This distinction is important because it dictates how ions combine to form neutral compounds.

The charge of an ion is due to the loss or gain of electrons. Metallic elements typically form cations by losing electrons, whereas nonmetals typically gain electrons to form anions.
For example, in the compound potassium chloride (KCl), potassium (K) acts as the cation with a single positive charge (K⁺), while chlorine (Cl) is the anion with a single negative charge (Cl^-).

During compound formation, the total positive charge of cations equals the total negative charge of anions, leading to a balanced, electrically neutral compound. Recognizing the charge on each ion enables students to write correct formulas and comprehend the underlying stoichiometric relationships.

Inorganic Compound Naming

The practice of inorganic compound naming involves creating names for compounds made mainly from elements other than carbon. This process is guided by a set of rules and conventions to produce a systematic name that conveys the composition of the compound.

Inorganic nomenclature involves stating the name of the cation followed by the anion. When naming an inorganic compound, you must consider the oxidation states, which are typically represented by Roman numerals in the name if the cation can have more than one ionic charge, such as iron (II) sulfate for FeSO₄ and iron (III) sulfate for Fe₂(SO₄)₃.

Another aspect is the use of prefixes and suffixes to indicate the number of atoms of each element in the compound, used primarily with non-metal compounds. For instance, diphosphorus pentoxide, P₂O₅, contains two atoms of phosphorus and five of oxygen.

Optimizing the Inorganic Naming Skill

The ability to name inorganic compounds accurately is developed through practice and application of the rules of systematic nomenclature. As one becomes familiar with these rules, they can quickly deduce the formula of a compound from its systematic name, and vice versa, laying a solid foundation for further study and application in the field of chemistry.