Problem 71 - Chemistry: The Central Science in SI Units, Global Edition

Question

Name the following ionic compounds: (a) \(\mathrm{Li}_{2} \mathrm{O},\) (b) \(\mathrm{FeCl}_{3}\), (c) \(\mathrm{NaClO}\) (d) \(\mathrm{CaSO}_{3}\), (e) \(\mathrm{Cu}(\mathrm{OH})_{2}\) (f) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\), (g) \(\mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}\) (h) \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\) (i) \(\mathrm{K}_{2} \mathrm{CrO}_{4},(\mathbf{j})\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\).

Step-by-Step Solution

Answer

(a) Lithium Oxide, (b) Iron(III) Chloride, (c) Sodium Hypochlorite, (d) Calcium Sulfite, (e) Copper(II) Hydroxide, (f) Iron(II) Nitrate, (g) Calcium Acetate, (h) Chromium(III) Carbonate, (i) Potassium Chromate, (j) Ammonium Sulfate.

Step 1: (a) Naming \(\mathrm{Li}_{2} \mathrm{O}\)

The compound \(\mathrm{Li}_{2} \mathrm{O}\) consists of two ions: lithium (Li) and oxygen (O). In the name, start with the cation, lithium. The anion oxygen exists as oxide. The name of this ionic compound is Lithium Oxide.

Step 2: (b) Naming \(\mathrm{FeCl}_{3}\)

The compound \(\mathrm{FeCl}_{3}\) consists of iron (Fe) and chlorine (Cl). Iron is a transition metal that requires a Roman numeral in its name to indicate its charge. In this case, the charge on the iron ion is +3 (since there are 3 chlorides with a charge of -1 each). Call the ion Iron(III). Chlorine forms the chloride anion. The compound is named Iron(III) Chloride.

Step 3: (c) Naming \(\mathrm{NaClO}\)

The compound \(\mathrm{NaClO}\) consists of sodium (Na) and the polyatomic anion called hypochlorite (ClO). The name of this ionic compound is Sodium Hypochlorite.

Step 4: (d) Naming \(\mathrm{CaSO}_{3}\)

The compound \(\mathrm{CaSO}_{3}\) consists of calcium (Ca) and the polyatomic anion called sulfite (SO\(_3\)). The name of this ionic compound is Calcium Sulfite.

Step 5: (e) Naming \(\mathrm{Cu}(\mathrm{OH})_{2}\)

The compound \(\mathrm{Cu}(\mathrm{OH})_{2}\) consists of copper (Cu) and the polyatomic anion called hydroxide (OH). Copper is a transition metal, and its charge is +2 (since there are two hydroxides with a charge of -1 each). The name of the copper ion is Copper(II). The name of this ionic compound is Copper(II) Hydroxide.

Step 6: (f) Naming \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\)

The compound \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) consists of iron (Fe) and the polyatomic anion called nitrate (NO\(_3\)). Iron, as a transition metal, has a charge of +2 in this compound (since there are two nitrates with a charge of -1 each). The name of the iron ion is Iron(II). This ionic compound is Iron(II) Nitrate.

Step 7: (g) Naming \(\mathrm{Ca}\left(\mathrm{CH}_{3}\mathrm{COO}\right)_{2}\)

The compound \(\mathrm{Ca}\left(\mathrm{CH}_{3}\mathrm{COO}\right)_{2}\) consists of calcium (Ca) and the polyatomic anion called acetate (CH\(_3\)COO). The name of this ionic compound is Calcium Acetate.

Step 8: (h) Naming \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\)

The compound \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\) consists of chromium (Cr) and the polyatomic anion called carbonate (CO\(_3\)). Chromium is a transition metal and has a charge of +3 in this compound (since there are three carbonates with a charge of -2 each). The name of the chromium ion is Chromium(III). This ionic compound is Chromium(III) Carbonate.

Step 9: (i) Naming \(\mathrm{K}_{2} \mathrm{CrO}_{4}\)

The compound \(\mathrm{K}_{2} \mathrm{CrO}_{4}\) consists of potassium (K) and the polyatomic anion called chromate (CrO\(_4\)). The name of this ionic compound is Potassium Chromate.

Step 10: (j) Naming \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\)

The compound \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\) consists of the polyatomic cation ammonium (NH\(_4\)) and the polyatomic anion called sulfate (SO\(_4\)). The name of this ionic compound is Ammonium Sulfate.

Key Concepts

Transition Metals

Transition metals are elements found in the center of the periodic table, specifically in groups 3 through 12. Unlike other elements, transition metals often have multiple oxidation states. This is because they have a unique configuration of electrons that can vary when they form compounds.
When naming ionic compounds containing transition metals, it's crucial to indicate the specific oxidation state of the metal by using Roman numerals in parentheses. For example, in the compound

• the iron in displays a +2 ion charge, so it's named Iron(II). If it had a +3 charge, it would be Iron(III).
• Another example is Copper in Copper(II) Hydroxide, where the copper ion has a charge of +2 reflective in the name Copper(II). These Roman numerals offer clarity about which ion is present in the compound, which is essential given the variable charges these metals can have.

Polyatomic Ions

Polyatomic ions are groups of atoms that carry a net charge because they have lost or gained electrons. Common in many compounds, they act as a single charged entity.

Some frequently encountered polyatomic ions include:

• Nitrate ( NO_3^-)
• Sulfate (SO_4^{2-})
• Acetate (CH_3CO_2^-)

When naming a compound with a polyatomic ion, the name of the ion remains unchanged. Take for instance In Iron(II) Nitrate, where nitrate indicates NO_3^-. Similarly, Calcium Acetate consists of the acetate ion CH_3CO_2^-. These ions maintain their integrity in chemical reactions, acting as a unit.

Nomenclature of Inorganic Compounds

Nomenclature refers to the systematic way in which compounds are named. To ensure clarity and consistency, chemists follow specific rules.

The process of naming involves identifying the cation (positive ion) and the anion (negative ion) in a compound. For simple ionic compounds, the cation is typically a metal ion. The anion is a non-metal ion or polyatomic ion.

• In compounds like the cation (e.g., lithium or calcium) is stated first. This is followed by the anion (oxide or sulfite, for example).
• When a polyatomic ion such as SO_4^{2-} (sulfate) or CO_3^{2-} (carbonate) is present, the name of the ion is used directly.
• For transition metals, it's essential to specify the charge of the metal ion using Roman numerals.

Thus, is correctly named as Iron(III) Chloride, including both the chemical identity and the oxidation state. By standardizing the naming system, communication about chemical substances becomes more precise and universal, facilitating a clearer understanding across different facets of chemistry.