Problem 23 - Chemistry and Chemical Reactivity

Question

Write the formulas for the four ionic compounds that can be made by combining each of the cations \(\mathrm{Na}^{+}\) and \(\mathrm{Ba}^{2+}\) with the anions \(\mathrm{CO}_{3}^{2-}\) and \(\mathrm{I}^{-}\). Name each of the compounds.

Step-by-Step Solution

Answer

The compounds are \( \mathrm{Na}_2\mathrm{CO}_3 \), \( \mathrm{NaI} \), \( \mathrm{BaCO}_3 \), and \( \mathrm{BaI}_2 \).

Step 1: Understand Cation-Anion Combinations

Each compound consists of one cation and one anion. We'll combine the given cations, \( \mathrm{Na}^{+} \) (sodium ion) and \( \mathrm{Ba}^{2+} \) (barium ion), with the anions, \( \mathrm{CO}_{3}^{2-} \) (carbonate ion) and \( \mathrm{I}^{-} \) (iodide ion) to form compounds.

Step 2: Combine \( \mathrm{Na}^{+} \) with Anions

First, pair the sodium ion \( \mathrm{Na}^{+} \) with each anion. - Combine \( \mathrm{Na}^{+} \) with \( \mathrm{CO}_{3}^{2-} \) to form \( \mathrm{Na}_{2}\mathrm{CO}_3 \) (sodium carbonate), as two sodium ions are needed to balance the charge of one carbonate ion.- Combine \( \mathrm{Na}^{+} \) with \( \mathrm{I}^{-} \) to form \( \mathrm{NaI} \) (sodium iodide), as one sodium ion balances the charge of one iodide ion.

Step 3: Combine \( \mathrm{Ba}^{2+} \) with Anions

Next, pair the barium ion \( \mathrm{Ba}^{2+} \) with each anion.- Combine \( \mathrm{Ba}^{2+} \) with \( \mathrm{CO}_{3}^{2-} \) to form \( \mathrm{BaCO}_3 \) (barium carbonate), as one barium ion perfectly balances the charge of one carbonate ion.- Combine \( \mathrm{Ba}^{2+} \) with \( \mathrm{I}^{-} \) to form \( \mathrm{BaI}_2 \) (barium iodide), as two iodide ions are needed to balance the charge of one barium ion.

Step 4: Summarize Compound Formulas and Names

List all formed compounds:1. \( \mathrm{Na}_{2}\mathrm{CO}_3 \) - Sodium Carbonate2. \( \mathrm{NaI} \) - Sodium Iodide3. \( \mathrm{BaCO}_3 \) - Barium Carbonate4. \( \mathrm{BaI}_2 \) - Barium Iodide

Key Concepts

Cations

Cations are positively charged ions. They are formed when an atom loses one or more electrons, resulting in a higher number of protons than electrons. This loss of electrons leads to a positive charge.
For example, in the problem,

• \( \mathrm{Na}^{+} \) is a cation formed when a sodium atom loses one electron.
• \( \mathrm{Ba}^{2+} \) is another cation formed when a barium atom loses two electrons.

Cations are typically metals and are crucial in forming ionic compounds by combining with negatively charged anions. They are usually smaller than their neutral atoms due to the loss of electron shells, increasing the pull of the remaining electrons towards the nucleus.

Anions

Anions, on the other hand, are negatively charged ions. These ions gain electrons, leading to more electrons than protons and a negative charge overall. Unlike cations, anions are often non-metals.
In the exercise, two anions are involved:

• \( \mathrm{CO}_{3}^{2-} \), known as the carbonate ion, has gained two electrons.
• \( \mathrm{I}^{-} \), or iodide ion, has gained one electron.

Anions combine with cations to form ionic compounds, balancing the overall charge of the compound. This process forms the stable ionic structures necessary for forming solids.

Chemical Formulas

Chemical formulas represent the composition of a compound by showing the types and numbers of atoms present. In the context of ionic compounds, they ensure that the total charge is balanced.
When writing ionic formulas:

• The charges of cations and anions must cancel each other out.
• Subscripts are used to indicate the number of each ion needed.

For example:

• \( \mathrm{Na}_{2}\mathrm{CO}_3 \) is formed by combining two \( \mathrm{Na}^{+} \) ions with one \( \mathrm{CO}_{3}^{2-} \) ion.
• \( \mathrm{BaI}_2 \) is formed by one \( \mathrm{Ba}^{2+} \) ion and two \( \mathrm{I}^{-} \) ions, ensuring neutrality.

This balance is key to writing correct and stable formulas.

Naming Compounds

Naming ionic compounds involves a straightforward system that reflects the ions involved. To name these compounds:
1. Start with the cation's name, which is simply the name of the element.
2. Follow with the anion's name. For monatomic anions, this is typically the element’s root with an “-ide” suffix.
In the exercise:

• \( \mathrm{NaI} \) is named sodium iodide, following straightforward naming rules.
• \( \mathrm{Na}_{2}\mathrm{CO}_3 \) is named sodium carbonate, using the polyatomic ion name carbonate.

For polyatomic ions like \( \mathrm{CO}_{3}^{2-} \), the ion's name is used without changes.
This system simplifies chemical communication, ensuring clarity across scientific disciplines.