Question

Name the following ions: (a) \(\mathrm{S}^{2-}\) (b) \(\mathrm{Sn}^{2+}\) (c) \(\mathrm{Sr}^{2+}\) (d) \(\mathrm{Mg}^{2+}\) (e) \(\mathrm{Au}^{+}\)

Short answer

(a) Sulfide, (b) Tin(II), (c) Strontium, (d) Magnesium, (e) Gold(I).

Step-by-step solution

Identify the Ion Type

There are two types of ions to identify in this problem: anions and cations. Anions have a negative charge, and cations have a positive charge. For each given chemical symbol, examine the charge to determine the type of ion it represents.

Naming the Anion

(a) The ion \(\mathrm{S}^{2-}\) is an anion as it carries a negative charge. For an anion formed from a single element, use the element's root name and add the suffix '-ide.' Thus, \(\mathrm{S}^{2-}\) is called 'sulfide.'

Naming Cations with Fixed Charges

(b) \(\mathrm{Sn}^{2+}\) is a cation. It's important to use the name of the element (tin) followed by the charge in Roman numerals in parentheses. Since tin can have different oxidation states, this cation is specifically known as 'tin(II).' The same naming convention applies to (c) \(\mathrm{Sr}^{2+}\) and (d) \(\mathrm{Mg}^{2+}\), each with a fixed charge. These are named simply by their element names: 'strontium' for \(\mathrm{Sr}^{2+}\) and 'magnesium' for \(\mathrm{Mg}^{2+}\).

Naming Cations with Variable Charges

(e) \(\mathrm{Au}^{+}\) is a cation from gold, which can have multiple oxidation states. Thus, use the element name (gold) followed by the charge in Roman numerals. Therefore, \(\mathrm{Au}^{+}\) is named 'gold(I).'

Key concepts

Anion Naming

Anion naming can be quite straightforward once you know what to look for. Anions are ions with a negative charge, and they are often formed when an atom gains one or more electrons. When naming monatomic (single-atom) anions, the name is derived from the element's root name, followed by the suffix "-ide." For example, the sulfide ion,

• "Sulfide" is the name given to the sulfur anion with a charge of 2- (\(\mathrm{S}^{2-}\)), originated from the element sulfur.

Remember: The change in the name to "sulfide" signifies its transformation from sulfur to its charged version as an anion.

Cation Naming

Cations are ions with a positive charge, formed usually when an atom loses electrons. The naming of cations depends on whether the element forms only one possible positive ion or multiple ones. For elements like magnesium (\(\mathrm{Mg}^{2+}\)) and strontium (\(\mathrm{Sr}^{2+}\)) that have a fixed single positive charge, the name of the element itself suffices for the cation name.

• Magnesium remains "magnesium," and strontium remains "strontium" as their chemical names.
• These are examples of cations with fixed charges.

For metals that can exhibit more than one possible positive charge, such as tin and gold, the oxidation state is specified in parentheses. Thus, tin (\(\mathrm{Sn}^{2+}\)) as "tin(II)" and gold (\(\mathrm{Au}^{+}\)) as "gold(I)" indicate their specific positive charges.

Ion Charges

Ion charges are crucial for understanding the properties and behaviors of ions in chemical compounds. An ion's charge is determined by the loss or gain of electrons relative to a neutral atom.

• When an atom loses electrons, it becomes a positively charged cation.
• Conversely, when an atom gains electrons, it becomes a negatively charged anion.

Understanding ion charges helps in predicting how ions will interact, attract, or repel each other in chemical compounds. It also assists in writing chemical formulas where the total positive charge must balance the total negative charge in a compound.

Oxidation States

Oxidation states are numbers assigned to elements in a chemical compound that describe their degree of oxidation. It is a kind of "bookkeeping" method used to track electron transfers in reactions involving ionic and molecular compounds. The oxidation state is often used interchangeably with oxidation number, and when naming ions, it is presented in Roman numerals.

• For example, in "tin(II)," the (II) indicates the tin atom has an oxidation state of +2, meaning it "wants to give away" two electrons or has lost two electrons.
• Similarly, "gold(I)" has an oxidation state of +1, indicating a loss of one electron.

Understanding oxidation states is vital for accurately naming cations that have multiple charges and predicting their chemical behavior.