Problem 35 - Chemistry: An Atoms-Focused Approach

Question

What are the names of the following ionic compounds? (a) \(\mathrm{NiCO}_{3} ;\) (b) \(\mathrm{NaCN} ;\) (c) \(\mathrm{LiHCO}_{3} ;\) (d) \(\mathrm{Ca}(\mathrm{ClO})_{2}\)

Step-by-Step Solution

Answer

Answer: The names of the given ionic compounds are: (a) Nickel Carbonate, (b) Sodium Cyanide, (c) Lithium Hydrogen Carbonate or Lithium Bicarbonate, and (d) Calcium Hypochlorite.

Step 1: Identify the cation and anion in compound (a) NiCO_3

In compound NiCO_3, the cation is Ni (Nickel) and the anion is CO_3^(2-) (Carbonate).

Step 2: Name the compound (a)

Since we have only one charge for Nickel here, the compound is called Nickel Carbonate.

Step 3: Identify the cation and anion in compound (b) NaCN

In compound NaCN, the cation is Na^+ (Sodium) and the anion is CN^- (Cyanide).

Step 4: Name the compound (b)

The compound is called Sodium Cyanide.

Step 5: Identify the cation and anion in compound (c) LiHCO_3

In compound LiHCO_3, the cation is Li^+ (Lithium) and the anion is HCO_3^- (Hydrogen Carbonate or Bicarbonate).

Step 6: Name the compound (c)

The compound is called Lithium Hydrogen Carbonate or Lithium Bicarbonate.

Step 7: Identify the cation and anion in compound (d) Ca(ClO)_2

In compound Ca(ClO)_2, the cation is Ca^(2+) (Calcium) and the anion is ClO^- (Hypochlorite).

Step 8: Name the compound (d)

The compound is called Calcium Hypochlorite.

Key Concepts

Cation and Anion Identification

To understand ionic compounds, it's essential to first identify the cation and the anion. A **cation** is a positively charged ion, which means it has lost electrons. On the other hand, an **anion** is negatively charged, meaning it has gained electrons.
For instance, in the compound \(\mathrm{NiCO}_{3}\), we can see:

• The **cation** is \(\mathrm{Ni}^{2+}\), which is Nickel.
• The **anion** is \(\mathrm{CO}_{3}^{2-}\), known as Carbonate.

Identifying these ions sets the foundation for naming the compounds correctly.
It's crucial to remember that metals typically form cations, whereas non-metals and polyatomic groups often form anions. This rule can help simplify the identification process.

Ionic Compound Nomenclature

Once cations and anions are identified, the next step in naming ionic compounds is following specific naming conventions. **Ionic compound nomenclature** involves combining the names of the cation and anion.
Here's a brief guide:

• **Name the cation first**: Use the metal's full name, like "Nickel" in Nickel Carbonate.
• **Name the anion second**: For monatomic anions, replace the end of the element's name with "-ide." For polyatomic ions, like "Carbonate," use their standard names.

If a metal can form ions of different charges, specify the charge with Roman numerals in brackets. For example, Iron (II) for \(\mathrm{Fe}^{2+}\). This naming system ensures consistent and clear identification of compounds.

Polyatomic Ions

When we mention **polyatomic ions**, we're talking about ions made up of two or more atoms that function as a single charged entity.
These are often encountered in ionic compounds and carry a specific name that must be memorized, such as "Carbonate" \(\mathrm{CO}_{3}^{2-}\) and "Cyanide" \(\mathrm{CN}^{-}\).

• Polyatomic ions always have a net charge, which can be positive or negative, although negative polyatomic ions are more common.
• They are crucial for forming various common ionic compounds and are found at the core of many substances used in everyday life.

To correctly name compounds containing them, always use the established name of the polyatomic group.
Familiarizing yourself with common polyatomic ions and their charges is a significant advantage when working with chemical formulas.

Chemical Formulas

Writing **chemical formulas** for ionic compounds involves using the symbols of the constituent ions and their appropriate quantities to balance charges.A well-writing formula ensures that the total positive charge equals the total negative charge, following the principle of charge neutrality.
Let's break it down:

• The symbol for the cation is written first followed by the anion's symbol.
• Use subscripts to denote the number of ions needed to balance the charge – for example, in \(\mathrm{Ca(ClO)}_{2}\), two hypochlorite ions \(\mathrm{ClO}^{-}\) balance the 2+ charge of one calcium ion \(\mathrm{Ca}^{2+}\).

To become proficient in chemical formulas, practice writing them from various ionic compounds until they become a second language. Remember, the accuracy of formulas is crucial in chemistry and helps in predicting the compound's properties and behavior.