Problem 66 - General Chemistry: Principles and Modern Applications

Question

Write an appropriate formula for each of the following: (a) hydroxylamine; (b) calcium hydrogen phosphate; (c) lithium nitride.

Step-by-Step Solution

Answer

The formulas are (a) hydroxylamine: \( NH_2OH \), (b) calcium hydrogen phosphate: \( CaHPO_4 \), (c) lithium nitride: \( Li_3N \).

Step 1: Formula for Hydroxylamine

Hydroxylamine is a compound comprised of hydrogen, oxygen, and nitrogen. The prefix 'hydroxyl-' signifies the presence of a hydroxyl group (OH) and 'amine' signifies the presence of an an amine group (NH2). Hence, the formula is \( NH_2OH \).

Step 2: Formula for Calcium Hydrogen Phosphate

Calcium hydrogen phosphate is made up of calcium (Ca), hydrogen (H), and phosphate (PO4). The name tells us that we have one calcium ion, two hydrogen ions and one phosphate ion. Hence, the formula is \( CaHPO_4 \).

Step 3: Formula for Lithium Nitride

Lithium nitride involves lithium (Li) and nitrogen (N). Lithium has +1 charge and Nitrogen has -3 charge. To neutralize the compound, three Lithium atoms bond with one Nitrogen atom. Hence, the formula is \( Li_3N \).

Key Concepts

Ionic Compounds

Ionic compounds are fascinating chemical structures resulting from the strong attraction between ions with opposite charges. For instance, when a metal such as lithium (Li), which tends to lose electrons and form positive ions, combines with a non-metal like nitrogen (N), known to gain electrons and form negative ions, an ionic compound is formed. The process involves a transfer of electrons from lithium to nitrogen.
This results in lithium becoming a positively charged ion (+1) and nitrogen a negatively charged ion (-3). To form a stable ionic compound, the charges must balance. Therefore, three lithium ions pair with one nitrogen ion. The formula for this compound is represented as \( Li_3N \). Ionic compounds like lithium nitride are characterized by their high melting and boiling points and the ability to conduct electricity when dissolved in water, due to the mobility of ions in a solution.
These compounds are often solid at room temperature and consist of crystalline lattice structures, further contributing to their stability and unique physical properties.

Molecular Compounds

Molecular compounds consist of molecules formed by atoms sharing electrons. Unlike ionic compounds, which involve a transfer of electrons, molecular compounds are the result of covalent bonds. These are bonds where atoms mutually share pairs of electrons.
Hydroxylamine, with the formula \( NH_2OH \), is an excellent example. It consists of hydrogen, nitrogen, and oxygen atoms. Here, the prefix 'amino' indicates the presence of an amine group, while 'hydroxyl' denotes a hydroxyl group. In this compound, nitrogen shares electrons with hydrogen atoms and is bonded with the hydroxyl group creating a molecule which is neutral.
Molecular compounds typically have lower melting and boiling points compared to ionic compounds, mainly because the forces between the molecules are weaker than the strong ionic bonds found in salts. Furthermore, they generally do not conduct electricity, as they lack free ions or charged particles when in solution.

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical substances. It involves specific rules to ensure each compound has a unique and widespread formula, crucial for effective communication in science.
For instance, the naming of calcium hydrogen phosphate (CaHPO_4) showcases this system in action. Calcium as a metallic element, has a charge of \(+2\), while the phosphate group (\(PO_4^{3-}\)) has a charge of \(-3\). The term "hydrogen phosphate" signifies that one hydrogen ion (+1) is also part of this compound, balancing the charges and forming a stable compound. The formula reflects the ionic balance and composition of the compound.
The systematic naming conventions involve identifying the metal and non-metal parts of ionic compounds and often using prefixes for molecular compounds to denote the number of atoms involved. Understanding chemical nomenclature is vital as it provides insights into the composition and properties of compounds, making chemistry universally comprehensible.