Question

The designations 1A through 8A used for certain families of the periodic table are helpful for predicting the charges on ions in binary ionic compounds. In these compounds, the metals generally take on a positive charge equal to the family number, while the nonmetals take on a negative charge equal to the family number minus eight. Thus the compound between sodium and chlorine contains \(\mathrm{Na}^{+}\) ions and \(\mathrm{Cl}^{-}\) ions and has the formula NaCl. Predict the formula and the name of the binary compound formed from the following pairs of elements. a. Ca and N b. \(\mathrm{K}\) and \(\mathrm{O}\) c. \(\mathrm{Rb}\) and \(\mathrm{F}\) d. Mg and S e. Ba and I f. Al and Se g. \(\mathrm{Cs}\) and \(\mathrm{P}\) h. In and Br

Short answer

The binary compounds formed are as follows: a. Calcium nitride: Ca3N2 b. Potassium oxide: K2O c. Rubidium fluoride: RbF d. Magnesium sulfide: MgS e. Barium iodide: BaI2 f. Aluminum selenide: Al2Se3 g. Cesium phosphide: Cs3P h. Indium bromide: InBr3

Step-by-step solution

Determine the charges on the ions

Using the family numbers of the given elements on the periodic table, determine the charges on the ions using the given rule: metals generally take on a positive charge equal to the family number, while the nonmetals have a negative charge equal to the family number minus eight.

Form balanced compounds

Determine the least common multiple of the charges (ignoring signs) and use it to form a balanced compound for each pair by taking the appropriate number of ions from each element.

Predict the names of the compounds

Using the IUPAC naming conventions, predict the names of the binary ionic compounds formed in step 2. Here are the answers for each of the given pairs: a. Ca and N Step 1: Ca has a +2 charge and N has a -3 charge. Step 2: The least common multiple of 2 and 3 is 6; to form a balanced compound, we need three Ca ions and two N ions. The formula is Ca3N2. Step 3: The name of the compound is calcium nitride. b. K and O Step 1: K has a +1 charge and O has a -2 charge. Step 2: The least common multiple of 1 and 2 is 2; to form a balanced compound, we need two K ions and one O ion. The formula is K2O. Step 3: The name of the compound is potassium oxide. c. Rb and F Step 1: Rb has a +1 charge and F has a -1 charge. Step 2: The least common multiple of 1 and 1 is 1; to form a balanced compound, we need one Rb ion and one F ion. The formula is RbF. Step 3: The name of the compound is rubidium fluoride. d. Mg and S Step 1: Mg has a +2 charge and S has a -2 charge. Step 2: The least common multiple of 2 and 2 is 2; to form a balanced compound, we need one Mg ion and one S ion. The formula is MgS. Step 3: The name of the compound is magnesium sulfide. e. Ba and I Step 1: Ba has a +2 charge and I has a -1 charge. Step 2: The least common multiple of 2 and 1 is 2; to form a balanced compound, we need one Ba ion and two I ions. The formula is BaI2. Step 3: The name of the compound is barium iodide. f. Al and Se Step 1: Al has a +3 charge and Se has a -2 charge. Step 2: The least common multiple of 3 and 2 is 6; to form a balanced compound, we need two Al ions and three Se ions. The formula is Al2Se3. Step 3: The name of the compound is aluminum selenide. g. Cs and P Step 1: Cs has a +1 charge and P has a -3 charge. Step 2: The least common multiple of 1 and 3 is 3; to form a balanced compound, we need three Cs ions and one P ion. The formula is Cs3P. Step 3: The name of the compound is cesium phosphide. h. In and Br Step 1: In has a +3 charge and Br has a -1 charge. Step 2: The least common multiple of 3 and 1 is 3; to form a balanced compound, we need one In ion and three Br ions. The formula is InBr3. Step 3: The name of the compound is indium bromide.

Key concepts

Periodic Table

The periodic table is a fundamental tool in chemistry, allowing us to understand the properties of elements and predict their behavior in chemical reactions. It organizes the elements into groups and periods based on shared characteristics and increasing atomic number. A key feature is its grouping into families or vertical columns, labeled from 1A to 8A (or simply 1 to 18 in modern conventions). Each family shares similar chemical properties and, more importantly for binary ionic compounds, similar ion charges.

For instance:

• Alkali metals (family 1A) typically form ions with a +1 charge.
• Alkaline earth metals (family 2A) typically form ions with a +2 charge.
• Halogens (family 7A) typically form ions with a -1 charge.

Understanding these charge patterns is essential for predicting the chemical formulas of binary ionic compounds. As you can see, by knowing the family number, one can often predict the ionic charge an element will take, which greatly assists in writing chemical formulas.

Ionic Charges

In chemistry, ionic charges are vital for understanding how elements combine to form compounds. Elements form ions, or charged particles when they gain or lose electrons to achieve a stable electron configuration, often mimicking the nearest noble gas. In binary ionic compounds, this charge difference allows elements to bond.Let's consider some examples from the exercise:

• Calcium (Ca) is in group 2A, and thus, loses two electrons to form \({\text{Ca}}^{2+}\).
• Nitrogen (N), from group 5A, gains three electrons to form \({\text{N}}^{3-}\). Hence, the compound formed, \( \text{Ca}_3\text{N}_2 \), balances the charges across the ions.

The principle of charge balance is simple: the total positive charge must equal the total negative charge in a compound. This ensures the compound is electrically neutral. To do this, one calculates the least common multiple of the charges to determine the number of each ion needed for a stable compound. Mastering ionic charges will lead to the accurate creation of various binary ionic compounds.

IUPAC Naming Conventions

The International Union of Pure and Applied Chemistry (IUPAC) provides standardized naming conventions which ensure clarity and consistency in chemical naming worldwide. These rules are crucial for naming binary ionic compounds.When naming such compounds, consider these guidelines:

• The metal (cation) is named first and retains its elemental name, such as "calcium" in \( \text{Ca}_3\text{N}_2 \).
• The nonmetal (anion) follows, with its base name modified to end in "-ide." For instance, nitrogen becomes "nitride."

Thus, the compound \( \text{Ca}_3\text{N}_2 \) is named "calcium nitride."

Consistent use of these conventions is essential in the scientific community, as it allows chemists worldwide to communicate more effectively. Memorizing and applying these rules will help in correctly naming vast arrays of ionic binary compounds.