Question

Give the names and charges of the cation and anion in each of the following compounds: (a) CuS, (b) \(\mathrm{Ag}_{2} \mathrm{SO}_{4}\) (c) \(\mathrm{Al}\left(\mathrm{ClO}_{3}\right)_{3}\) (d) \(\mathrm{Co}(\mathrm{OH})_{2}\) (e) \(\mathrm{PbCO}_{3}\).

Short answer

(a) The cation is Copper (II) with a charge of +2, and the anion is Sulfide with a charge of -2. (b) The cation is Silver with a charge of +1, and the anion is Sulfate with a charge of -2. (c) The cation is Aluminum with a charge of +3, and the anion is Chlorate with a charge of -1. (d) The cation is Cobalt (II) with a charge of +2, and the anion is Hydroxide with a charge of -1. (e) The cation is Lead (II) with a charge of +2, and the anion is Carbonate with a charge of -2.

Step-by-step solution

Identify the cation and anion

In this compound, Cu (Copper) is the cation and S (Sulfide) is the anion.

Determine the charges

Copper is in group 11 of the periodic table and can have multiple charges, in this case it has a charge of +2 (because Sulfide has a charge of -2). Sulfur is in group 16, which means it gains 2 electrons, so the charge of Sulfide is -2.

Answer

The cation is Copper (II) with a charge of +2, and the anion is Sulfide with a charge of -2. (b) \(\mathrm{Ag}_{2} \mathrm{SO}_{4}\)

Identify the cation and anion

In this compound, Ag (Silver) is the cation and \(\mathrm{SO}_{4}\) (Sulfate) is the anion.

Determine the charges

Silver is in group 11 of the periodic table and has a charge of +1. Sulfate is a polyatomic ion with a known charge of -2.

Answer

The cation is Silver with a charge of +1, and the anion is Sulfate with a charge of -2. (c) \(\mathrm{Al}\left(\mathrm{ClO}_{3}\right)_{3}\)

Identify the cation and anion

In this compound, Al (Aluminum) is the cation and \(\mathrm{ClO}_{3}\) (Chlorate) is the anion.

Determine the charges

Aluminum is in group 13 of the periodic table, which gives it a charge of +3. Chlorate is a polyatomic ion with a known charge of -1.

Answer

The cation is Aluminum with a charge of +3, and the anion is Chlorate with a charge of -1. (d) \(\mathrm{Co}(\mathrm{OH})_{2}\)

Identify the cation and anion

In this compound, Co (Cobalt) is the cation and \(\mathrm{OH}\) (Hydroxide) is the anion.

Determine the charges

Cobalt is a transition metal and can have multiple charges, in this case it has a charge of +2 (because Hydroxide has a charge of -1 and there are 2 Hydroxide ions). Hydroxide is a polyatomic ion with a known charge of -1.

Answer

The cation is Cobalt (II) with a charge of +2, and the anion is Hydroxide with a charge of -1. (e) \(\mathrm{PbCO}_{3}\)

Identify the cation and anion

In this compound, Pb (Lead) is the cation and \(\mathrm{CO}_{3}\) (Carbonate) is the anion.

Determine the charges

Lead is a transition metal and can have multiple charges, in this case it has a charge of +2 (because Carbonate has a charge of -2). Carbonate is a polyatomic ion with a known charge of -2.

Answer

The cation is Lead (II) with a charge of +2, and the anion is Carbonate with a charge of -2.

Key concepts

Cation and Anion Identification

Understanding which ions are cations and which are anions is critical for analyzing ionic compounds. In chemical compounds, the **cation** is the positively charged ion, while the **anion** is negatively charged. Cations are typically metals that lose electrons, such as Aluminum (Al) in \( \mathrm{Al}(\mathrm{ClO}_{3})_{3} \).Here, the aluminum ion gives up three electrons, resulting in a +3 charge. Anions, on the other hand, gain electrons. For instance, the Chlorate ion \( \mathrm{ClO}_{3}^{-} \)gains an electron, leading to a charge of -1. Identifying which element or group in a chemical formula is the cation or anion is usually the first step in understanding ionic compounds. In \( \mathrm{CuS} \),Copper (Cu) is the cation, and Sulfide (S) is the anion.

Charge Determination

Determining the charge of ions is a key part of dissecting ionic compounds. The total charge in a compound must be neutral, so the charges of the cations and anions must balance. Cations like Silver (Ag) in \( \mathrm{Ag}_{2}\mathrm{SO}_{4} \)typically have a fixed charge of +1, whereas others like Copper (Cu) can vary. In \( \mathrm{CuS} \),Copper adopts a +2 charge to balance the Sulfide ion's -2 charge.Anions such as Sulfate \( \mathrm{SO}_{4}^{2-} \)carry their charges inherently due to the combination of elements they consist of. When determining charges for transition metals, you'll focus on ensuring the overall neutrality of the compound. For \( \mathrm{PbCO}_{3} \),for example, Lead (Pb) must be +2 since Carbonate \( \mathrm{CO}_{3}^{2-} \)is -2.

Transition Metals

Transition metals, like Cobalt (Co) in \( \mathrm{Co}(\mathrm{OH})_{2} \),are unique among metals because they can exhibit more than one oxidation state or charge. This means they can lose different numbers of electrons depending on their chemical context. Such variability requires careful attention when naming and balancing ionic equations. For example, Cobalt often has charges of +2 or +3. In \( \mathrm{Co}(\mathrm{OH})_{2} \),Cobalt carries a charge of +2. The hydroxide ions (each with a charge of -1) balance this charge, showing why understanding the behavior of transition metals is crucial in predicting and verifying the properties of ionic compounds. Understanding transition metals often involves context clues obtained from the formula and the charges of known anions.

Polyatomic Ions

Polyatomic ions are clusters of atoms that act as a single charged entity. They are common in many compounds and usually have a more complex structure than simple ions. An example is the Sulfate ion \( \mathrm{SO}_{4}^{2-} \),part of \( \mathrm{Ag}_{2} \mathrm{SO}_{4} \).These ions keep their charge when forming compounds.Polyatomic ions such as Chlorate \( \mathrm{ClO}_{3}^{-} \)or Carbonate \( \mathrm{CO}_{3}^{2-} \)are often memorized due to their prevalence and the distinct chemical properties they impart to compounds. The familiarity with these ions helps in predicting the formation and characteristics of various ionic compounds, emphasizing the need for understanding both charge conservation and the structural reasoning behind these entities within compounds.