Ionic vs. Covalent Compounds and Solubility: Study Guide

Unit: Ionic vs. Covalent Compounds and Solubility

Vocabulary and Key Concepts

This section introduces essential terms and definitions related to ionic and covalent compounds, solubility, and the classification of matter.

• Ionic Compound: A chemical compound composed of ions held together by electrostatic forces termed ionic bonding. Typically formed between metals and nonmetals.

• Covalent Compound: A compound where atoms share electrons, usually formed between nonmetals.

• Solute: The substance that is dissolved in a solution.

• Solvent: The substance that dissolves the solute, often present in greater amount.

• Solution: A homogeneous mixture of two or more substances.

• High Concentration: A solution with a large amount of solute relative to solvent.

• Low Concentration: A solution with a small amount of solute relative to solvent.

• Metal: An element that is lustrous, conducts electricity, and is malleable.

• Nonmetal: An element that is not lustrous, has a low melting point, and does not conduct electricity well.

Classifying Matter

Matter can be classified based on its composition and properties. Understanding the differences between elements, compounds, and mixtures is fundamental in chemistry.

• Element: A pure substance consisting of only one type of atom.

• Compound: A substance formed when two or more elements are chemically bonded together.

• Mixture: A combination of two or more substances that are not chemically bonded.

Order of Types of Matter (from simplest to most complex):

1. Element

2. Atom

3. Compound

Comparison: Atoms are the smallest units of elements, while compounds consist of atoms of different elements bonded together. Mixtures contain two or more substances physically combined.

Ionic vs. Covalent Compounds

Ionic and covalent compounds differ in their bonding, properties, and composition. Recognizing these differences is crucial for predicting chemical behavior.

• Ionic Bond: Formed by the transfer of electrons from a metal to a nonmetal, resulting in positive and negative ions.

• Covalent Bond: Formed by the sharing of electrons between nonmetals.

• Properties of Ionic Compounds:

  • High melting and boiling points

  • Conduct electricity when dissolved in water

  • Usually soluble in water

• Properties of Covalent Compounds:

  • Lower melting and boiling points

  • Do not conduct electricity in water

  • May be soluble or insoluble in water

Example: Sodium chloride (NaCl) is an ionic compound; water (H2O) is a covalent compound.

Identifying Ionic and Covalent Compounds

Compounds can be identified as ionic or covalent based on their composition and the types of elements involved.

Compound	Metal or Nonmetal	Ionic or Covalent Bond?
SO2	Nonmetal	Covalent
F2	Nonmetal	Covalent
MgBr2	Metal + Nonmetal	Ionic
CaO	Metal + Nonmetal	Ionic
H2O	Nonmetal	Covalent
AlF3	Metal + Nonmetal	Ionic

Naming Ionic and Covalent Compounds

Naming conventions differ for ionic and covalent compounds.

• Ionic Compounds: Name the metal (cation) first, then the nonmetal (anion) with an '-ide' ending.

• Covalent Compounds: Use prefixes to indicate the number of atoms (mono-, di-, tri-, etc.) and end the second element with '-ide'.

Example: CO2 is carbon dioxide; NaCl is sodium chloride.

Solubility and Solutions

Solubility refers to the ability of a substance to dissolve in a solvent. Solutions are classified based on the amount of solute dissolved.

• Soluble: A substance that can dissolve in a solvent.

• Insoluble: A substance that cannot dissolve in a solvent.

• Saturated Solution: Contains the maximum amount of solute that can dissolve at a given temperature.

• Unsaturated Solution: Contains less solute than can be dissolved at a given temperature.

Example: Table salt (NaCl) is soluble in water; sand is insoluble in water.

Solubility Graphs

Solubility graphs show how the solubility of substances changes with temperature. These graphs are useful for predicting how much solute can dissolve at different temperatures.

• To identify a saturated solution, find the point on the graph where the amount of solute matches the solubility at a given temperature.

• Compounds with steeper curves increase solubility more rapidly with temperature.

Example: At 60°C, the solubility of KNO3 is higher than that of NaCl.

Calculating Percent Mass of Solute in Solution

The percent mass of a solute in a solution is calculated using the following formula:

• Formula: $\text{Percent by mass} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100$

• To find the concentration in ppm (parts per million): $\text{ppm} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 10^6$

Example: If 5 grams of MgCl2 are dissolved in 95 grams of water, the percent by mass is:

• $\frac{5}{100} \times 100 = 5\%$

Summary Table: Properties of Ionic vs. Covalent Compounds

Property	Ionic Compounds	Covalent Compounds
Bond Type	Transfer of electrons	Sharing of electrons
Elements Involved	Metal + Nonmetal	Nonmetal + Nonmetal
Melting/Boiling Point	High	Low
Electrical Conductivity	Conducts in solution	Does not conduct
Solubility in Water	Usually soluble	Variable

Additional info:

• Some context and definitions were expanded for clarity and completeness.

• Tables were inferred and completed based on standard chemistry knowledge.