The key difference between ionic and molecular compounds is that the ionic compounds have electrostatic attraction forces between cations and anions whereas the molecular compounds have only covalent chemical bonds between the atoms.
Chemical elements can join with each other to form chemical compounds. The elements bind together via chemical bonds that have ionic or covalent characteristics. If the compounds have ionic bonds, we call them as ionic compounds, and if they have covalent bonds, then they are molecular compounds. Hence, the key difference between ionic and molecular compounds lies upon the chemical bonding between atoms.
CONTENTS
1. Overview and Key Difference
2. Whare are Ionic Compounds
3. What are Molecular Compounds
4. Side by Side Comparison – Ionic vs Molecular Compounds in Tabular Form
5. Summary
What are Ionic Compounds?
Ionic compounds are the chemical compounds that have cations and anions that bind to each other via ionic bonding. Hence, there are electrostatic attraction forces between cations and anions. However, the compound has an overall neutral charge because the total charge of cations is neutralized by the total charge of anions. These ions can be either monoatomic or polyatomic.
Usually, the ionic compounds containing hydrogen ion (H+) as the cation are “acids”. In contrast, basic ions such as hydroxide ion (OH–) is present in bases. If there are no hydrogen ions or hydroxide ions in the ionic compound, then we name it as a “salt”.
Figure 01: Ionic Compound of Sodium Chloride, which is a Salt
Some ionic compounds such as salts form from acid-base neutralization reactions. some compounds form via evaporation of the solvent, precipitation reactions, solid-state reactions, freezing, electron transfer reactions between metals and nonmetals, etc. Typically, these compounds have high melting and boiling points. Most of the times they are hard and brittle. In their solid state, almost all the ionic compounds are electrical insulators, and they can become highly conductive when dissolved in a solvent such as water because then the cations and anions can move freely.
What are Molecular Compounds?
Molecular compounds are chemical compounds containing atoms bonded to each other via covalent chemical bonds. Therefore, these compounds form when atoms share their unpaired electrons with each other. The atoms involved in this electron sharing have similar electronegativity values.
Figure 02: A diagram of a Triatomic Molecule having Covalent Bonds between the three Atoms
Typically, molecular compounds have relatively low melting and boiling points because the atoms are not strongly attached to each other. Similarly, these compounds are soft and relatively flexible. Compared to ionic compounds, these molecular compounds are highly flammable. This is because almost all the flammable substances are molecular compounds consisting of carbon and hydrogen atoms. Unlike ionic compounds, they cannot conduct electricity when dissolved in a solvent because there are no available ions to separate after dissolving.
What is the Difference Between Ionic and Molecular Compounds?
Ionic compounds are the chemical compounds that have cations and anions that bind to each other via ionic bonding while molecular compounds are chemical compounds containing atoms bonded to each other via covalent chemical bonds. Hence, the difference between ionic and molecular compounds lies upon the nature of chemical bonding. That is; the key difference between ionic and molecular compounds is that the ionic compounds have electrostatic attraction forces between cations and anions whereas the molecular compounds have only covalent chemical bonds between the atoms.
As another important difference between ionic and molecular compounds, the ionic compounds are hard and brittle while molecular compounds are soft and relatively flexible. This is mainly because the atoms of ionic compounds are held together tightly by ionic bonds whereas in molecular compounds atoms attach to each other relatively loosely. Moreover, the melting and boiling points of ionic compounds are very high in comparison to that of molecular compounds.
Summary – Ionic vs Molecular Compounds
Ionic compounds have ionic bonds while molecular compounds have covalent bonds. Hence, the key difference between ionic and molecular compounds is that the ionic compounds have electrostatic attraction forces between cations and anions whereas the molecular compounds have only covalent chemical bonds between the atoms.
Reference:
1. Helmenstine, Anne Marie, Ph.D. “Covalent or Molecular Compound Properties.” ThoughtCo, Jun. 7, 2018. Available here
2. “Ionic Compound.” Wikipedia, Wikimedia Foundation, 20 Oct. 2018. Available here
Image Courtesy:
1.”Sodium-chloride-3D-ionic”By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia
2.”Carbon-dioxide-3D-vdW”By Jacek FH – Own work (CC BY-SA 3.0) via Commons Wikimedia