Question

Borax is a common household and commercial chemical. Look up the chemical formula for borax. What is the anion in borax and the correct chemical name for the anion? (Hint: It is a polyatomic ion.)

Short answer

The anion in borax is tetraborate, \( \text{B}_4\text{O}_7^{2-} \).

Step-by-step solution

Write Down the Chemical Formula of Borax

The chemical formula for borax is \( \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \). It is a hydrated form of sodium borate.

Identify the Polyatomic Ion

In borax, the polyatomic ion is \( \text{B}_4\text{O}_7^{2-} \). This can be seen from the borax formula \( \text{Na}_2\text{B}_4\text{O}_7 \), where the sodium ions \( \text{Na}^+ \) balance the charge of the \( \text{B}_4\text{O}_7^{2-} \) ion.

Determine the Chemical Name of the Anion

The anion \( \text{B}_4\text{O}_7^{2-} \) is known as tetraborate. This is the correct chemical name for the polyatomic ion found in borax.

Key concepts

Polyatomic Ions

Polyatomic ions are ions that consist of two or more atoms bonded together, carrying a net positive or negative charge. They're like tiny molecular compounds with a charge, ready to interact with other substances in chemical reactions.
A common example of a polyatomic ion is the sulfate ion, \( \text{SO}_4^{2-} \), which features sulfur and oxygen atoms tightly linked together with an overall negative charge.
Polyatomic ions can form stable ionic compounds by combining with ions of the opposite charge, much like what happens in borax.

Tetraborate Anion

The tetraborate anion is a specific type of polyatomic ion found in borax. Its chemical formula is \( \text{B}_4\text{O}_7^{2-} \).
This ion contains four boron atoms bonded to seven oxygen atoms, creating a complex structure that holds an overall charge of \( 2- \).
To neutralize this charge, it often pairs with positive ions, like sodium ions \( \text{Na}^+ \), creating stable compounds.
Additionally, tetraborate plays a role in many applications, from detergent formulations to acting as a flux in metallurgy. Its functionality is a result of this unusual structure and charge.

Sodium Borate

Sodium borate, commonly referred to as borax, is an essential component in various household and industrial contexts.
The chemical formula for borax is \( \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \), indicating it is a hydrated compound of sodium ions and tetraborate anions.
Each unit of borax contains two sodium ions \( \text{Na}^+ \) that balance the charge of one tetraborate ion \( \text{B}_4\text{O}_7^{2-} \). The presence of ten water molecules signifies it as a hydrated salt, which greatly influences its physical properties, such as solubility and crystal structure.

Chemical Formula Analysis

Chemical formula analysis involves breaking down a compound into its basic components to understand its composition and structure.
In the case of borax, analyzing its chemical formula \( \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \) unveils a balanced mix of sodium ions, tetraborate anions, and water molecules.

• \( \text{Na}_2 \): Indicates two sodium atoms present.
• \( \text{B}_4 \): Comprises four boron atoms.
• \( \text{O}_7 \): Consists of seven oxygen atoms.
• \( \cdot\ 10\text{H}_2\text{O} \): Represents the ten water molecules attached to the compound.

This formula reveals how the different elements and ions interact within borax, providing insights into its chemical behavior and properties.