Naming Monatomic Anions and Systematic Names for Anions

Monatomic Anions

Systematic Naming of Anions

Monatomic anions are negatively charged ions formed from single atoms. Their systematic names are derived by modifying the element's base name and adding the suffix -ide.

• Base Name: The root of the element's name.

• Suffix: Add -ide to the base name.

• Charge: The charge is indicated by the ion's superscript.

Example Table: Common Monatomic Anions

Element	Base Name	Anion Name	Symbol
Fluorine	fluor	fluoride	F-
Chlorine	chlor	chloride	Cl-
Bromine	brom	bromide	Br-
Iodine	iod	iodide	I-
Oxygen	ox	oxide	O2-
Sulfur	sulf	sulfide	S2-
Selenium	selen	selenide	Se2-
Phosphorus	phosph	phosphide	P3-
Nitrogen	nitr	nitride	N3-

Example: Naming the Selenide Ion

• Symbol: Se2-

• Name: Selenide ion

• Systematic Name: Selenide

• Formation: Selenium atom gains two electrons to form Se2-.

Example Equation:

• $\text{Se} + 2e^- \rightarrow \text{Se}^{2-}$

Practice: Identifying the Oxide Ion

• Symbol: O2-

• Name: Oxide ion

• Explanation: Oxygen atom gains two electrons to form O2-.

Practice: Naming Ionic Compounds

When naming ionic compounds, the cation (positive ion) is named first, followed by the anion (negative ion) with its modified ending.

• Example: Magnesium ion (Mg2+) and Phosphide ion (P3-) combine to form magnesium phosphide.

• Formula: $\text{Mg}_3\text{P}_2$

• Systematic Name: Magnesium phosphide

Additional info: The notes also reference the importance of recognizing the correct charge and name for each ion when forming compounds.