Question

Supply the Stock system name for each of the following monoatomic cations: (a) \(\mathrm{Ba}^{2+}\) (b) \(\mathrm{Zn}^{2+}\) (c) \(\mathrm{Co}^{3+}\) (d) \(\mathrm{Cu}^{+}\)

Short answer

(a) Barium ion (b) Zinc ion (c) Cobalt(III) ion (d) Copper(I) ion

Step-by-step solution

Identify Cation Type

Determine whether the cation is from a metal with a fixed charge or a variable charge. (a) Barium is a Group 2 element and forms a fixed charge (b) Zinc always forms a 2+ charge (c) Cobalt can have variable charges (d) Copper can have variable charges

Stock Name for Fixed Charge

For cations with fixed charges, use the element name directly as the Stock system name. (a) Barium ion (b) Zinc ion

Determine Charge for Variable Charge Metals

For each metal with variable charges, determine the specific charge: (c) Cobalt is given as 3+, so it is cobalt(III) (d) Copper is given as 1+, so it is copper(I)

Write Stock System Name for Variable Charge

Write the Stock system name by including the charge in Roman numerals in parentheses: (c) Cobalt will be cobalt(III) ion (d) Copper will be copper(I) ion

Key concepts

Monoatomic Cations

Monoatomic cations are positively charged ions that consist of a single atom. These ions form when an atom loses one or more electrons. For example:

• The ion \({\text{Ba}}^{2+}\) is a monoatomic cation formed from barium, which loses two electrons.
• Zinc, with the ion \({\text{Zn}}^{2+}\), similarly loses two electrons to form a stable cation.

Unlike polyatomic cations, which consist of multiple atoms bonded together, monoatomic cations are simple. They are typically metals on the left side of the periodic table. The charge of a monoatomic cation is indicated by a superscript number and plus sign, showing how many electrons have been lost.

Fixed Charge Cations

Fixed charge cations are metal ions that have a single, unchangeable charge when they form. This means that whenever such an element becomes a cation, it assumes a specific charge. For example, elements in Group 1 of the periodic table will always have a +1 charge. Elements like barium, which is in Group 2, form fixed cations with a 2+ charge, like \({\text{Ba}}^{2+}\). Zinc, although not in Group 1 or 2, also has a fixed charge of 2+, forming the ion \({\text{Zn}}^{2+}\). The consistency of these charges eliminates the need for Roman numerals in naming.

Variable Charge Cations

Variable charge cations are ions that can have more than one possible charge. This phenomenon is common with transition metals, as they can lose different numbers of electrons. Transition metals, like cobalt and copper, do not have fixed charges. Instead, their charges depend on the specific chemical reaction or environment they are in.

• Cobalt can form 2+ or 3+ ions, such as \({\text{Co}}^{2+}\) or \({\text{Co}}^{3+}\).
• Copper can form \({\text{Cu}}^{2+}\) or \({\text{Cu}}^{+}\).

These metals need their charge specified when naming their cations, requiring the Stock system naming with Roman numerals to indicate the precise ionic charge.

Stock System Naming

The Stock system of nomenclature is essential for naming ions that have variable charges. This system uses Roman numerals to state the oxidation number (charge) of a metal ion in a compound. When applying the Stock system, follow these simplified steps: 1. Identify whether the metal is a fixed charge or variable charge cation. 2. For variable charge cations, note the ion's charge. 3. Write the element name followed by the charge in Roman numerals in parentheses. 4. If the charge is fixed, simply use the element name followed by "ion." For instance, cobalt with a 3+ charge becomes cobalt(III) ion, and copper with a 1+ charge is referred to as copper(I) ion. This method ensures clarity and precision, particularly when dealing with metals that can exhibit more than one possible charge.

Chemistry Education

Understanding chemistry nomenclature, such as naming ions using the Stock system, is a fundamental aspect of chemistry education. It helps students grasp crucial concepts about electrons, oxidation states, and the periodic table. Knowing the difference between fixed and variable charge cations deepens comprehension of chemical behavior. Educators aim to make such topics more digestible by breaking down complex ideas into manageable pieces. New learners often start with the periodic table to understand element placement and their typical charges. Effective chemistry education unfolds the patterns in periodic elements, making the naming conventions intuitive. By demystifying such basics, educational resources prepare students for more advanced chemical study and problem-solving in future courses.