Question

Supply a systematic name for each of the following binary ionic compounds: (a) \(\mathrm{LiBr}\) (b) \(\mathrm{SrI}_{2}\) (c) \(\mathrm{Na}_{3} \mathrm{~N}\) (d) \(\mathrm{AlF}_{3}\)

Short answer

(a) Lithium bromide; (b) Strontium iodide; (c) Sodium nitride; (d) Aluminum fluoride.

Step-by-step solution

Identify the Cation and Anion

Each of the given compounds is composed of two parts: a cation (positively charged ion) and an anion (negatively charged ion). Identify the cation and anion in each formula: (a) For \( \text{LiBr} \), lithium (Li) is the cation and bromine (Br) is the anion.(b) For \( \text{SrI}_2 \), strontium (Sr) is the cation and iodine (I) is the anion.(c) For \( \text{Na}_3 \text{N} \), sodium (Na) is the cation and nitrogen (N) is the anion.(d) For \( \text{AlF}_3 \), aluminum (Al) is the cation and fluorine (F) is the anion.

Name the Cation

For each compound, write the name of the cation. Cations formed by metals typically retain the name of the element:(a) The cation in \( \text{LiBr} \) is "lithium."(b) The cation in \( \text{SrI}_2 \) is "strontium."(c) The cation in \( \text{Na}_3 \text{N} \) is "sodium."(d) The cation in \( \text{AlF}_3 \) is "aluminum."

Name the Anion

For each anion, use the root of the element’s name followed by the suffix "-ide":(a) The anion in \( \text{LiBr} \) is "bromide."(b) The anion in \( \text{SrI}_2 \) is "iodide."(c) The anion in \( \text{Na}_3 \text{N} \) is "nitride."(d) The anion in \( \text{AlF}_3 \) is "fluoride."

Combine Cation and Anion Names

Combine the respective names of the cation and the anion to form the full names of the compounds:(a) \( \text{LiBr} \) is named "lithium bromide."(b) \( \text{SrI}_2 \) is named "strontium iodide."(c) \( \text{Na}_3 \text{N} \) is named "sodium nitride."(d) \( \text{AlF}_3 \) is named "aluminum fluoride."

Key concepts

Binary Ionic Compounds

Binary ionic compounds are chemical compounds composed of two different elements. As the name suggests, these compounds are made up of two parts: a cation (a positively charged ion) and an anion (a negatively charged ion). These ions are held together by ionic bonds, which occur due to the electrostatic attraction between the oppositely charged ions.

In binary ionic compounds, you typically have metals paired with nonmetals. Metals will form cations by losing electrons, while nonmetals will form anions by gaining electrons. For example, in the compound \( \mathrm{LiBr} \), lithium (Li) is a metal that gives away an electron to become a \( \text{Li}^+ \) cation, and bromine (Br) accepts an electron to become a \( \text{Br}^- \) anion.

Understanding binary ionic compounds is essential for grasping how basic chemical reactions and bonding occur. These compounds are foundational in chemical nomenclature and are often the first type students encounter when learning about chemistry.

Cation and Anion Identification

Identifying cations and anions in a chemical formula is a critical step in naming ionic compounds. Cations are positively charged because they lose electrons, while anions are negatively charged because they gain electrons. In a compound, the cation is usually written first, followed by the anion.

Let's look at a few examples:

• In \( \mathrm{LiBr} \), lithium (Li) is the cation, and bromine (Br) is the anion.
• In \( \mathrm{SrI}_2 \), strontium (Sr) is the cation, and iodine (I) is the anion.
• For \( \mathrm{Na}_3 \mathrm{~N} \), sodium (Na) is the cation, and nitrogen (N) is the anion.
• In \( \mathrm{AlF}_3 \), aluminum (Al) is the cation, and fluorine (F) is the anion.

By recognizing the metal and nonmetal elements, or more simply, identifying the positions of these elements in the periodic table, one can easily determine which element will be the cation and which will be the anion.

This understanding helps build the foundational knowledge required to correctly name and formulate diverse chemical compounds.

Chemical Nomenclature

Chemical nomenclature is the systematic approach to naming chemical substances. It's like learning the rules of a new language. For binary ionic compounds, this means combining the names of the cation and the anion.

Here's how you name them:

• First, write the name of the cation, which is the same as the element name. For example, \( \text{Li}^+ \) is "lithium," and \( \text{Sr}^{2+} \) is "strontium."
• Next, write the name of the anion. Take the root of the element's name and add the suffix "-ide." For instance, \( \text{Br}^- \) becomes "bromide," and \( \text{I}^- \) becomes "iodide."

Combine the two: - "lithium bromide" for \( \mathrm{LiBr} \)
- "strontium iodide" for \( \mathrm{SrI}_2 \)
- "sodium nitride" for \( \mathrm{Na}_3 \mathrm{~N} \)
- "aluminum fluoride" for \( \mathrm{AlF}_3 \)
By sticking to these rules, chemists worldwide can communicate unambiguously about different substances. Consistency in naming compounds is vital for science and industry to ensure that everyone is speaking the same "chemical language."