Write the formula for each of the following compounds: a. zinc chloride b. \(\operatorname{tin}(\mathrm{IV})\) fluoride c. calcium nitride d. aluminum sulfide e. mercury(1) selenide f. silver iodide

Understanding ionic compounds is fundamental in chemistry. An ionic compound is formed when atoms of different elements transfer electrons from one to another, creating positively charged ions called cations, and negatively charged ions called anions. These ions are held together by strong electrostatic forces known as ionic bonds. Common examples include table salt (sodium chloride, NaCl) and the compounds given in the exercise, such as zinc chloride (ZnCl_2) and calcium nitride (Ca_3N_2).

Since the resulting compound must be electrically neutral, the total positive charge must balance out the total negative charge. This concept leads us naturally into our next topic - charge balance in compounds.

Finding the Right Ratio

Charge balance in compounds is the cornerstone of determining the correct formula for ionic compounds. Each ion has a set of oxidation states, or charges, it can adopt. When writing a chemical formula, it is crucial to use the charges of the ions to determine the ratio of ions that will result in a compound with a net charge of zero.

For instance, if we look at aluminum sulfide, aluminum (Al) forms a 3+ ion, and sulfur (S) forms a 2- ion. To achieve charge neutrality, we need two 3+ aluminum ions to balance three 2- sulfur ions, resulting in the formula Al_2S_3. By applying the charge balance rule, we can deduce the correct formulas for the compounds in the exercise, ensuring that the total positive charge equals the total negative charge.

• To reinforce these principles, remember to start with the known charges of the ions.
• Write the charges above the symbols of the elements.
• Determine the lowest whole number ratio that balances the total positive and negative charges.

The systematic naming of chemical compounds is known as chemical nomenclature. It provides a uniform way to identify substances and alleviate confusion. Ionic compounds, like the ones we see in the exercise, have a straightforward naming system.

The name of the metallic ion (the cation) comes first, followed by the name of the non-metallic ion (the anion) with an 'ide' suffix. In cases where the metal can have more than one charge, such as with tin(IV) fluoride (SnF_4), roman numerals in parentheses indicate the charge of the metal ion. This also applies to compounds with transition metals, such as mercury(1) selenide, where mercury has multiple stable oxidation states.

Correct chemical nomenclature enables seamless communication among scientists and provides insight into the composition of a compound. By knowing the rules, students can confidently derive the names of ionic compounds from their chemical formulas or vice versa. Key points include:

• For metals with a single oxidation state, simply name the metal followed by the anion.
• For metals with multiple oxidation states, indicate the charge with roman numerals.
• Use the 'ide' suffix for the anion unless it is a complex polyatomic ion.