Question

Classify each compound as ionic or molecular. $$ \text { a. }\mathrm{CO}_{2} \quad \text { b. } \mathrm{NiCl}_{2} \quad \text { c. Nal } \quad \text { d. } \mathrm{PCl}_{3} $$

Short answer

a. CO2 is molecular. b. NiCl2 is ionic. c. NaI is ionic. d. PCl3 is molecular.

Step-by-step solution

Identify the Types of Elements

Determine whether the compound is composed of a metal and a nonmetal (ionic) or only nonmetals (molecular/covalent).

Classify CO2

Carbon (C) and oxygen (O) are both nonmetals. Since CO2 consists only of nonmetals, it is classified as a molecular compound.

Classify NiCl2

Nickel (Ni) is a metal and chlorine (Cl) is a nonmetal. Because NiCl2 is made up of a metal and a nonmetal, it is classified as an ionic compound.

Classify NaI

Sodium (Na) is a metal and iodine (I) is a nonmetal. The compound NaI, consisting of a metal and a nonmetal, is classified as an ionic compound.

Classify PCl3

Phosphorus (P) and chlorine (Cl) are both nonmetals. PCl3 is composed only of nonmetals, so it is classified as a molecular compound.

Key concepts

Ionic and Molecular Compounds

Understanding the differences between ionic and molecular compounds is key to mastering the basics of chemistry. Ionic compounds, like the salt on your dinner table, are composed of metals and nonmetals. They form through a transfer of electrons from the metal to the nonmetal, creating ions that are positively and negatively charged, and bond due to these opposite charges.

On the other hand, molecular compounds, also known as covalent compounds, involve nonmetals sharing electrons. Think of it like a team project where everyone contributes equally. These compounds are typically found as gases, liquids, or low melting point solids at room temperature.

Examples in Daily Life

Table salt (NaCl) is a common ionic compound, while the oxygen you breathe (O2) is a molecular compound.

Chemical Bonding

Chemical bonding is the glue that holds compounds together. There are several types of chemical bonds, with ionic and covalent being two primary forms. Ionic bonds are formed through the attraction between oppositely-charged ions, which is like magnets sticking together. Covalent bonds, on the other hand, happen when atoms share pairs of electrons to fill their outer shells and achieve stability, similar to two friends sharing a pie to make sure everyone gets a slice.

Understanding the type of bond can give insights into the properties of the compound, such as melting and boiling points, conductivity, and solubility.

Bond Strength

Generally, ionic bonds are stronger than covalent bonds due to the charge attraction, which affects how easily a compound can be broken down.

Metal and Nonmetal Chemistry

Metals and nonmetals have distinct chemical behaviors, largely stemming from their position in the periodic table and the structure of their electron shells. Metals, like copper or iron, tend to lose electrons and form cations (positively charged ions). They are often shiny, malleable, and good conductors of electricity and heat.

Nonmetals, such as sulfur and carbon, typically gain electrons, forming anions (negatively charged ions). They are often found in all three states of matter at room temperature and have a wide variety of chemical properties.

Reaction Tendencies

Metals often react by ceding their outer electrons, while nonmetals tend to attract more electrons to fill their own shells. This fundamental difference is crucial in the formation of ionic compounds.

Compound Composition

The composition of a compound tells us what elements it contains and in what ratios. In our examples, CO2 means one carbon atom is bonded to two oxygen atoms, and PCl3 indicates one phosphorus atom bonded to three chlorine atoms. This ratio is critical for understanding the properties of the compound, such as its reactivity, toxicity, and role in biological systems.

These chemical formulas act like recipes in chemistry, guiding us through the creation or interaction with other substances.

Understanding Formulas

Reading and interpreting chemical formulas correctly is crucial for predicting compound behavior and interaction in various chemical reactions, making it one of the fundamental skills in chemistry.