Understanding Chemical Nomenclature: Naming Single-Atom Negative Ions

In chemistry, naming conventions, or nomenclature, help us identify substances based on their composition. When atoms gain electrons, they become negatively charged ions called anions. Single-atom ions are formed from a single atom.

The question asks for the specific suffix added to the name of an element when it forms a single-atom negative ion. Let's examine the options provided:

• -ous: This suffix is typically used to indicate the lower oxidation state of a metal in older nomenclature (e.g., ferrous chloride for FeCl₂ where iron is +2). It is not used for naming single-atom negative ions.
• -ic: This suffix is used to indicate the higher oxidation state of a metal in older nomenclature (e.g., ferric chloride for FeCl₃ where iron is +3). Like '-ous', it is not used for naming single-atom negative ions.
• -onium: This suffix is used for certain polyatomic positive ions (cations), such as ammonium (\(\text{NH}_4^+\)) or hydronium (\(\text{H}_3\text{O}^+\)). It is not used for naming single-atom negative ions.
• -ide: This is the standard suffix added to the stem of the element's name to denote a single-atom negative ion. For example:
  • Chlorine (\(\text{Cl}\)) forms the chloride ion (\(\text{Cl}^-\)).
  • Oxygen (\(\text{O}\)) forms the oxide ion (\(\text{O}^{2-}\)).
  • Nitrogen (\(\text{N}\)) forms the nitride ion (\(\text{N}^{3-}\)).
  • Sulfur (\(\text{S}\)) forms the sulfide ion (\(\text{S}^{2-}\)).
  • Bromine (\(\text{Br}\)) forms the bromide ion (\(\text{Br}^-\)).

Therefore, the suffix used for single-atom negative ions is -ide.

Naming Single-Atom Anions: The -ide Suffix

Let's look at some common examples of how single-atom negative ions are named using the -ide suffix.

As you can see from the table, the suffix -ide is consistently used for these single-atom negative ions.

Revision Table: Suffixes in Chemical Names

Additional Information on Ion Nomenclature

While -ide is used for single-atom anions, it is also used for a few common polyatomic anions, like hydroxide (\(\text{OH}^-\)), cyanide (\(\text{CN}^-\)), and peroxide (\(\text{O}_2^{2-}\)). However, for most polyatomic oxyanions (ions containing oxygen), suffixes like -ate and -ite are used, indicating different numbers of oxygen atoms bonded to a central atom. Cations (positive ions) formed from metals are simply named after the metal element (e.g., sodium ion \(\text{Na}^+\), calcium ion \(\text{Ca}^{2+}\)). Polyatomic cations have specific names, often ending in -onium, as mentioned earlier.

Understanding these naming rules is crucial for correctly identifying chemical compounds and writing chemical formulas.