Question

Write the formulas and names of the hydrides of the following second-period elements: \(\mathrm{Li}, \mathrm{C}, \mathrm{N}, \mathrm{O}, \mathrm{F}\) Predict their reactions with water.

Short answer

Hydrides: LiH, CH4, NH3, H2O, HF. Reactions with water: LiH produces H2 and LiOH; CH4 does not react; NH3 forms NH4+ and OH-; HF forms hydrofluoric acid.

Step-by-step solution

Identify Hydrides

For each element, determine the chemical formula of its corresponding hydride.- Lithium (Li) forms lithium hydride: \( \text{LiH} \).- Carbon (C) forms methane: \( \text{CH}_4 \).- Nitrogen (N) forms ammonia: \( \text{NH}_3 \).- Oxygen (O) forms water but typically creates hydrides in compound form with alkali and alkaline earth metals. Here, consider water: \( \text{H}_2\text{O} \).- Fluorine (F) forms hydrogen fluoride: \( \text{HF} \).

Predict Reaction with Water for LiH

LiH reacts with water to release hydrogen gas and generate a basic solution:\[ \text{LiH} + \text{H}_2\text{O} \rightarrow \text{LiOH} + \text{H}_2 \].

Predict Reaction with Water for CH4

\( \text{CH}_4 \) is nonpolar and does not react with water under normal conditions.

Predict Reaction with Water for NH3

Ammonia (NH3) dissolves in water to form an alkaline solution, creating ammonium hydroxide:\[ \text{NH}_3 + \text{H}_2\text{O} \rightarrow \text{NH}_4^+ + \text{OH}^- \].

Predict Reaction with Water for H2O

H2O is water itself, thus the question of its reaction with water is redundant.

Predict Reaction with Water for HF

Hydrogen fluoride dissolves in water to form hydrofluoric acid:\[ \text{HF} + \text{H}_2\text{O} \rightarrow \text{H}_3\text{O}^+ + \text{F}^- \].

Key concepts

Hydrides

Hydrides are compounds formed when hydrogen binds with another element. These compounds serve as essential models in inorganic chemistry due to their simple structures and varied reactions. Understanding hydrides can make the study of more complex chemical reactions easier.
For the second-period elements in the exercise, we identify the following hydrides:

• Lithium (Li): Forms lithium hydride (\( ext{LiH}\)).
• Carbon (C): Forms methane (\( ext{CH}_4\)).
• Nitrogen (N): Forms ammonia (\( ext{NH}_3\)).
• Oxygen (O): Typically forms water (\( ext{H}_2 ext{O}\)), but reacts as a hydride in specific contexts.
• Fluorine (F): Forms hydrogen fluoride (\( ext{HF}\)).

Hydrides are crucial because they highlight the diverse bonding modes possible with hydrogen, from ionic to covalent to complex network structures.

Second-Period Elements

The second-period elements of the periodic table, ranging from lithium (Li) to neon (Ne), are integral to the foundation of chemistry. These elements belong to the second row of the periodic table and show how elemental properties evolve with increasing atomic number.
Focusing on the specific elements in this exercise, we discuss:

• Lithium (Li): As the lightest metal, it forms a strong ionic bond with hydrogen.
• Carbon (C): The backbone of organic chemistry, carbon forms versatile covalent bonds, exemplified by methane (\( ext{CH}_4\)).
• Nitrogen (N): Forms stable covalent bonds and is essential for the formation of ammonia (\( ext{NH}_3\)), a key industrial chemical.
• Oxygen (O): Known for forming polar covalent bonds, crucial in the structure of water.
• Fluorine (F): The most electronegative element, forming ionic compounds with hydrogen.

These elements demonstrate a range of chemical behaviors as they transition from metallic to nonmetallic character across the period.

Chemical Reactions with Water

Reactions between hydrides and water are fascinating due to the varied outcomes they produce. Understanding these interactions helps explain fundamental chemical processes in nature. Here’s a look at how each hydride interacts with water:

• \( ext{LiH}\): Reacts with water to form lithium hydroxide (\( ext{LiOH}\)) and hydrogen gas (\( ext{H}_2\)), displaying a basic reaction.
• \( ext{CH}_4\): Methane does not react with water under normal circumstances due to its nonpolar nature.
• \( ext{NH}_3\): Dissolves in water to create ammonium hydroxide (\( ext{NH}_4 ext{OH}\)), a basic solution.
• \( ext{H}_2 ext{O}\): Being water itself, it is the solvent and is not considered a reactant.
• \( ext{HF}\): Forms hydrofluoric acid when dissolved in water, producing \( ext{H}_3 ext{O}^+\) and \( ext{F}^-\), a strong acidic solution.

These reactions illustrate how hydrides can exhibit a range of chemical behaviors, from neutrality and basicity to acidity.

Inorganic Chemistry

Inorganic chemistry deals with the properties and behavior of inorganic compounds, which include not only simple molecules but also salts and minerals. This branch of chemistry is distinct from organic chemistry and provides insights into the vast array of chemical reactions and compositions found in the world.
Some key concepts related to the exercise include:

• Bonding and Structure: Understanding ionic and covalent bonds, as seen in compounds like \( ext{LiH}\) and \( ext{CH}_4\).
• Reaction Mechanisms: Examining how hydrides interact with water to form new compounds or release gases.
• Periodic Trends: Observing how elements such as Lithium to Fluorine vary in behavior and properties due to their position in the periodic table.
• Chemical Properties: Analyzing factors like electronegativity and reactivity which influence compound formation and reaction.

By exploring inorganic chemistry, students gain the ability to predict and understand chemical reactions, aiding in the broader comprehension of chemical phenomena.