Write formulas for the ionic compounds formed from (a) \(\mathrm{Zn}^{2+}\) and hydroxide ion, (b) \(\mathrm{Ag}^{+}\) and chromate ion, (c) \(\mathrm{Ba}^{2+}\) and sulfite ion, (d) \(\mathrm{Rb}^{+}\) and sulfate ion, and (e) \(\mathrm{Li}^{+}\) and bicarbonate ion.

Chemical bonds are the forces that hold atoms or ions together in compounds. There are several types of chemical bonds, with ionic bonds being a common type, especially when forming compounds with metals and nonmetals. In an ionic bond, one atom, typically a metal, loses electrons to become a positively charged ion, while the other atom, often a nonmetal, gains those electrons to become a negatively charged ion. This exchange leads to a strong electromagnetic force between the oppositely charged ions, resulting in the formation of an ionic compound. Understanding the nature of ionic bonds is fundamental to predicting the composition of an ionic compound and writing its formula correctly.

For example, in the exercise provided, zinc (Zn) loses two electrons to form a Zn²⁺ ion, and the hydroxide ion (OH^-) already possesses an extra electron. The Zn²⁺ ion and two OH^- ions combine to form the neutral ionic compound zinc hydroxide (Zn(OH)₂) through an ionic bond.

Valency refers to the combining power of an element, specifically the number of electrons an atom can lose, gain, or share to form a chemical bond. In ionic compounds, valency is closely related to the ionic charge—the numerical value of the electric charge on an ion. This charge determines how ions will combine to form a neutral compound. The charges must balance out so that the total positive charge equals the total negative charge.

For instance, the valency of a Zn²⁺ ion is 2, meaning it can form bonds with two negatively charged ions each with a valency of 1, such as OH^- ions. Similarly, since silver (Ag⁺) has a charge of +1, it will need to bind with two units of the chromate ion (CrO₄^2-), which has a charge of -2, to balance the charges and create an electrically neutral compound.

Writing chemical formulas is a method of conveying the proportions of ions that form a compound. You have to reflect the balance of ionic charges between the cations (positive ions) and anions (negative ions). The steps for writing formulas include determining the ionic charge of each ion and then balancing the total positive and negative charges. The simplest ratio of ions that leads to a neutral compound is used in the formula.

As shown in the solutions, the formula for the compound formed from Ba²⁺ and SO₃^2- is BaSO₃. They combine in a 1:1 ratio since their charges are equal and opposite. Understanding the process of writing chemical formulas is crucial for students as it not only helps with homework assignments but also establishes a foundational skill for future scientific studies.