Question

Name each of the following ionic compounds: (a) \(\mathrm{K}_{2} \mathrm{S}\) (b) \(\cos \mathrm{O}_{4}\) (c) \(\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\) (d) \(\mathrm{Ca}(\mathrm{ClO})_{2}\)

Short answer

(a) Potassium sulfide, (b) Cobalt(II) sulfate, (c) Ammonium phosphate, (d) Calcium hypochlorite.

Step-by-step solution

Identify the first compound

The formula given is \( \mathrm{K}_{2} \mathrm{S} \). This compound consists of potassium (\( \mathrm{K} \)) and sulfur (\( \mathrm{S} \)). Potassium is a metal and therefore, it forms an ionic bond with sulfur, which is a non-metal. The name of the compound is potassium sulfide.

Identify the second compound

The formula given is \( \mathrm{CoSO}_{4} \). This compound consists of cobalt (\( \mathrm{Co} \)) and the sulfate ion (\( \mathrm{SO}_{4}^{2-} \)). Since cobalt can have multiple oxidation states, we typically include its oxidation state in Roman numerals if not specified; however, without additional context, we assume the common name: cobalt(II) sulfate.

Identify the third compound

The formula is \( \left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4} \). This compound consists of ammonium ions \( \mathrm{NH}_{4}^{+} \) and phosphate ions \( \mathrm{PO}_{4}^{3-} \). Therefore, its name is ammonium phosphate.

Identify the fourth compound

The formula is \( \mathrm{Ca}(\mathrm{ClO})_{2} \). This compound consists of calcium (\( \mathrm{Ca} \)) and hypochlorite ions (\( \mathrm{ClO}^{-} \)). Therefore, the name of the compound is calcium hypochlorite.

Key concepts

Potassium Sulfide

Potassium sulfide is an ionic compound formed by the combination of potassium and sulfur. Potassium, symbolized as \( \mathrm{K} \), is a metal element found in group 1 of the periodic table, known as the alkali metals. These metals have a high tendency to lose one electron to form positive ions, or cations. In this case, each potassium atom loses one electron to form a \( \mathrm{K}^+ \) ion.
Sulfur, on the other hand, is a non-metal, represented by the symbol \( \mathrm{S} \). It belongs to group 16 and typically gains two electrons to become a negatively charged ion, or anion, specifically \( \mathrm{S}^{2-} \).
Together, two potassium ions \( (2 \times \mathrm{K}^+) \) balance the negative charge of one sulfide ion \( (\mathrm{S}^{2-}) \) to form the neutral compound potassium sulfide, \( \mathrm{K}_2 \mathrm{S} \). This chemical reaction leads to an ionic bond, where electrons are transferred from potassium to sulfur, resulting in a stable electronic arrangement.

Cobalt(II) Sulfate

Cobalt(II) sulfate is an example of a transition metal compound, which often have multiple oxidation states. Cobalt, with the symbol \( \mathrm{Co} \), can exhibit different charges, but in cobalt(II) sulfate, it is in a +2 oxidation state, hence the name cobalt(II). This is expressed using Roman numerals in parentheses following the element name.
This compound couples cobalt ions with the sulfate ion, \( \mathrm{SO}_4^{2-} \). The sulfate ion is a polyatomic ion, which means it is a charged species formed from a group of covalently bonded atoms.
In \( \mathrm{CoSO}_4 \), one \( \mathrm{Co}^{2+} \) ion balances the charge of one \( \mathrm{SO}_4^{2-} \) ion, resulting in a neutral ionic compound without the need for additional ions or charges.

Ammonium Phosphate

Ammonium phosphate is composed of ammonium ions \( \mathrm{NH}_4^+ \) and phosphate ions \( \mathrm{PO}_4^{3-} \). The ammonium ion is a common polyatomic cation, where nitrogen is surrounded by four hydrogen atoms, leading to an overall positive charge.
The phosphate ion, \( \mathrm{PO}_4^{3-} \), is a polyatomic anion comprised of one phosphorus atom covalently bonded to four oxygen atoms. This ion carries a -3 charge.
To create a neutral compound, three ammonium ions \( (3 \times \mathrm{NH}_4^+) \) are needed to balance the negative charge of one phosphate ion \( (\mathrm{PO}_4^{3-}) \). This results in the formation of ammonium phosphate, \( (\mathrm{NH}_4)_3 \mathrm{PO}_4 \), a compound often used as a fertilizer due to its high nitrogen and phosphorus content.

Calcium Hypochlorite

Calcium hypochlorite, \( \mathrm{Ca}(\mathrm{ClO})_2 \), is an ionic compound made up of calcium ions and hypochlorite ions. Calcium, represented by \( \mathrm{Ca} \), is an alkaline earth metal that tends to donate two electrons, forming a \( \mathrm{Ca}^{2+} \) ion, a cation. It belongs to group 2 in the periodic table.
The hypochlorite ion, \( \mathrm{ClO}^- \), is a polyatomic anion consisting of one chlorine atom bonded to an oxygen atom. This anion carries a single negative charge.
The formula \( \mathrm{Ca}(\mathrm{ClO})_2 \) indicates that one calcium ion \( \mathrm{Ca}^{2+} \) pairs with two hypochlorite ions \( (2 \times \mathrm{ClO}^-) \) to achieve charge neutrality in the compound. Calcium hypochlorite is commonly used as a disinfectant, especially in swimming pools, due to its ability to release chlorine when dissolved in water.