Problem 35 - Chemistry The Molecular Science

Question

Although not a transition element, lead can form two cations: \(\mathrm{Pb}^{2+}\) and \(\mathrm{Pb}^{4+}\). Write the formulas for the compounds of these ions with the chloride ion.

Step-by-Step Solution

Answer

The compounds are \(\mathrm{PbCl}_2\) and \(\mathrm{PbCl}_4\).

Step 1: Understanding the Problem

We need to find the chemical formulas for compounds formed by lead ions (\(\mathrm{Pb}^{2+}\) and \(\mathrm{Pb}^{4+}\)) when they combine with chloride ions (\(\mathrm{Cl}^{-}\)). Each chloride ion carries a \(-1\) charge.

Step 2: Finding the Formula for \(\mathrm{Pb}^{2+}\) with Chloride

First, consider the \(\mathrm{Pb}^{2+}\) ion, which has a \(+2\) charge. Since each chloride ion has a \(-1\) charge, two chloride ions are needed to balance the charge of one \(\mathrm{Pb}^{2+}\) ion. Thus, the formula for the compound is \(\mathrm{PbCl}_2\).

Step 3: Finding the Formula for \(\mathrm{Pb}^{4+}\) with Chloride

Next, consider the \(\mathrm{Pb}^{4+}\) ion, which has a \(+4\) charge. To balance this, four chloride ions, each with a \(-1\) charge, are needed. Therefore, the chemical formula for this compound is \(\mathrm{PbCl}_4\).

Key Concepts

Understanding Lead Ions

Lead ions are an interesting part of chemistry because they can exist in different forms, notably \(\mathrm{Pb}^{2+}\) and \(\mathrm{Pb}^{4+}\). These ions are derived from lead, which despite not being a transition metal, displays variable oxidation states just like them. This unique feature of lead allows it to form different ions.

• Lead can lose either two or four electrons resulting in different cations.
• \(\mathrm{Pb}^{2+}\) and \(\mathrm{Pb}^{4+}\) are both stable forms found in various compounds.
• The ability of lead to form different ions is key to its capacity to create multiple chemical compounds.

Lead, known by its symbol 'Pb', was historically used in pipes and paints, but due to its toxicity, its use has been minimized.This chemical diversity of lead allows it to combine with other ions such as the chloride ion, forming stable compounds with distinct properties.

Understanding Chloride Ions

The chloride ion, \(\mathrm{Cl}^{-}\), is quite simple compared to lead ions. It is formed when a chlorine atom gains an extra electron. This gives the chloride ion a negative charge of \-1\, making it anionic.

• Chloride ions are essential in forming many ionic compounds.
• They often pair with positive ions (cations) to balance charges in a compound.
• Chloride ions have applications in everyday life, from table salt (NaCl) to disinfectants like bleach.

Because of their simplicity, chloride ions frequently combine with various metal ions including lead. This pairing is important for a wide range of chemical substances present in both nature and manufactured products.

Formation of Ionic Compounds

Ionic compounds are composed of positive and negative ions. The concept is simple: opposites attract. When ions like lead \(\mathrm{Pb}^{2+}\) or \(\mathrm{Pb}^{4+}\) meet chloride ions \(\mathrm{Cl}^{-}\), they form compounds.The main characteristics are:

• Ionic compounds have high melting and boiling points.
• They are generally solid due to the strong attraction between opposite charges.
• These compounds conduct electricity when dissolved in water.

For example, when \(\mathrm{Pb}^{2+}\) combines with chloride ions, two chloride ions are needed to balance it, forming \(\mathrm{PbCl}_2\). Similarly, \(\mathrm{Pb}^{4+}\) needs four chloride ions, resulting in \(\mathrm{PbCl}_4\).Understanding how ions combine to form stable ionic compounds helps in grasping larger chemistry concepts and exploring the diversity of chemical reactions and materials around us.