Problem 65 - Chemistry The Central Science

Question

Predict whether each of the following compounds is molecular or ionic: (a) \(\mathrm{B}_{2} \mathrm{H}_{6},(\mathbf{b}) \mathrm{CH}_{3} \mathrm{OH},(\mathbf{c}) \mathrm{LiNO}_{3},(\mathbf{d}) \mathrm{Sc}_{2} \mathrm{O}_{3}\) (e) \(\mathrm{CsBr},(\mathbf{f}) \mathrm{NOCl},(\mathbf{g}) \mathrm{NF}_{3},(\mathbf{h}) \mathrm{Ag}_{2} \mathrm{SO}_{4}\)

Step-by-Step Solution

Answer

(a) B2H6: molecular, (b) CH3OH: molecular, (c) LiNO3: ionic, (d) Sc2O3: ionic, (e) CsBr: ionic, (f) NOCl: molecular, (g) NF3: molecular, (h) Ag2SO4: ionic.

Step 1: (a) B2H6 (Boron Hydrogen)

As Boron (B) and Hydrogen (H) are both non-metal elements, the compound B2H6 is molecular.

Step 2: (b) CH3OH (Methanol)

Since Carbon (C), Hydrogen (H), and Oxygen (O) are all non-metal elements, the compound CH3OH is molecular.

Step 3: (c) LiNO3 (Lithium Nitrate)

Because Lithium (Li) is a metal element, and Nitrogen (N) and Oxygen (O) are non-metal elements, the compound LiNO3 is ionic.

Step 4: (d) Sc2O3 (Scandium Oxide)

As Scandium (Sc) is a metal element and Oxygen (O) is a non-metal element, the compound Sc2O3 is ionic.

Step 5: (e) CsBr (Cesium Bromide)

Since Cesium (Cs) is a metal element and Bromine (Br) is a non-metal element, the compound CsBr is ionic.

Step 6: (f) NOCl (Nitrosyl Chloride)

Given that Nitrogen (N), Oxygen (O), and Chlorine (Cl) are all non-metal elements, the compound NOCl is molecular.

Step 7: (g) NF3 (Nitrogen Trifluoride)

As Nitrogen (N) and Fluorine (F) are both non-metal elements, the compound NF3 is molecular.

Step 8: (h) Ag2SO4 (Silver Sulfate)

Because Silver (Ag) is a metal element, and Sulfur (S) and Oxygen (O) are non-metal elements, the compound Ag2SO4 is ionic.

Key Concepts

Chemical Bonding

Chemical bonding is a fundamental concept in understanding how different atoms connect to form compounds. It primarily involves two types of bonds: ionic and covalent. Ionic bonds occur when there is a transfer of electrons from a metal to a non-metal. This results in oppositely charged ions attracting each other. On the other hand, covalent bonds form when two non-metals share electrons. This sharing allows both atoms to attain a stable electron configuration.

A compound's behavior, including solubility and melting points, can often be attributed to the types of bonds it contains. Understanding whether a compound is ionic or covalent can thus help predict its properties. In short, chemical bonding is crucial as it determines how different substances are held together and interact with each other.

Compound Classification

Based on the types of elements involved and the nature of the chemical bonds, compounds are classified into two main categories: molecular (or covalent) compounds and ionic compounds.

Molecular compounds are formed from non-metal atoms. They are usually present as discrete molecules, like ext{(a) ext{B}_2 ext{H}_6} and ext{(b) ext{CH}_3 ext{OH}} in the exercise. These compounds tend to have lower melting and boiling points due to the relatively weak interactions between the molecules.

Ionic compounds result from metals reacting with non-metals, creating a lattice structure held together by strong ionic bonds. Examples include ext{(c) ext{LiNO}_3} and ext{(d) ext{Sc}_2 ext{O}_3} from the exercise. These compounds generally exhibit high melting and boiling points and often dissolve in water to form electrolytes.

Metal and Non-metal Elements

To identify whether a compound is molecular or ionic, understanding the distinction between metal and non-metal elements is essential. Metals, like lithium ( ext{Li}), scandium ( ext{Sc}), and cesium ( ext{Cs}) in the exercise, are typically found on the left side and center of the periodic table. They tend to lose electrons easily, forming positive ions, which is a key characteristic in ionic compound formation.

Non-metals, such as nitrogen ( ext{N}), oxygen ( ext{O}), and chlorine ( ext{Cl}), are located on the right side of the periodic table. These elements usually gain or share electrons in bonds, forming structures like ext{(e) ext{CsBr}} for ionic and ext{(f) ext{NOCl}} for molecular compounds.

The combination of metal and non-metal elements signifies a likelihood of ionic bonding, while compounds solely containing non-metals often point toward molecular bonding. Understanding these differences can simplify predicting compound classifications and their properties.