Ionic compounds form through the transfer of electrons between atoms, resulting in charged ions held together by electrostatic forces, while molecular compounds consist of covalently bonded atoms sharing electrons, forming discrete molecules.
- Ionic compounds are composed of ions that are held together by electrostatic forces.
- Molecular compounds are composed of molecules that are held together by covalent bonds.
- Ionic compounds have higher melting and boiling points than molecular compounds and are soluble in water.
Ionic Compounds vs Molecular Compounds
Ionic compounds are formed by the ionic bonds in which the atoms are electrostatically attracted to one another. They have interaction of cations and anions in them. While molecular compounds are formed by covalent bonds, in which the electrons are shared by the atoms forming the bond.
To understand the difference better, you need to understand the basic terminology well. Two or more two atoms of different elements combine to form a molecule, which is the basic unit of a compound.
Every compound is different in terms of properties. This is due to the fact that every element that a compound consists of possesses different properties. Electronegativity is also one of the most important terms to know.
Electronegativity is the tendency of an atom of an element to attract the electrons of other elements towards its core. A compound may be polar or non-polar, and this entirely depends on the electronegativity of the elements.
|Electrostatic attraction between oppositely charged ions (cations and anions)
|Sharing of electrons between atoms
|Formed by metal(s) and nonmetal(s)
|Usually formed by nonmetals only, but can also include hydrogen with other elements
|State at room temperature
|Mostly gases, liquids, or solids (depends on molecule)
|Melting and boiling points
|High melting and boiling points
|Generally lower melting and boiling points than ionic compounds
|Conduct electricity when melted or dissolved in water
|Generally non-conductive, except for some special cases
|Solubility in water
|Generally soluble in water
|Generally less soluble in water than ionic compounds
|NaCl (table salt), CaCl2 (calcium chloride), MgO (magnesium oxide)
|H2O (water), CO2 (carbon dioxide), CH4 (methane), NH3 (ammonia)
What are Ionic Compounds?
Ionic compounds are a type of chemical compound characterized by the presence of ions, which are atoms or groups of atoms that have gained or lost electrons, thereby acquiring a net electrical charge. These compounds are formed through the interaction between atoms of different elements with significantly different electronegativities.
In an ionic compound, one or more electrons are transferred from a metal atom (which has a low electronegativity) to a non-metal atom (which has a high electronegativity). This transfer of electrons leads to the formation of positively charged ions, known as cations, and negatively charged ions, known as anions. The attraction between these oppositely charged ions results in the formation of ionic bonds, which are electrostatic forces of attraction holding the ions together in a lattice structure.
The crystal lattice structure of ionic compounds contributes to their characteristic properties, including high melting and boiling points, as well as brittleness when solid. Ionic compounds also tend to be soluble in polar solvents, such as water, due to the attraction between the ions and the polar molecules of the solvent.
Common examples of ionic compounds include sodium chloride (table salt), potassium chloride (used in fertilizers and food additives), calcium carbonate (found in limestone and antacid medications), and magnesium sulfate (Epsom salt). These compounds play essential roles in various industrial, agricultural, and biological processes due to their distinct chemical properties and reactivities.
What are Molecular Compounds?
Molecular compounds are substances composed of individual molecules, where atoms are held together by covalent bonds. In these compounds, atoms share electrons to achieve stable electron configurations. This sharing allows for the formation of discrete units known as molecules.
Key features of molecular compounds include:
- Covalent Bonding: Atoms in molecular compounds share one or more pairs of electrons to complete their valence shells. This sharing creates a bond between the atoms, known as a covalent bond.
- Neutral Overall Charge: Unlike ionic compounds, which consist of positively and negatively charged ions, molecular compounds are electrically neutral. The sharing of electrons allows atoms to achieve stable electron configurations without forming ions.
- Low Melting and Boiling Points: Molecular compounds have lower melting and boiling points compared to ionic compounds. This is because the intermolecular forces between molecules (such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding) are weaker than the electrostatic forces between ions in ionic compounds.
- Variable Composition Ratios: Molecular compounds can have variable ratios of elements within a molecule. This variability arises from the ability of atoms to form multiple covalent bonds with different partners, leading to a wide range of molecular structures and compositions.
- Examples: Examples of molecular compounds include water (H2O), carbon dioxide (CO2), methane (CH4), ammonia (NH3), and sulfur dioxide (SO2), among many others.
Main Differences Between Ionic Compounds and Molecular Compounds
- Chemical Bonding:
- Ionic Compounds: Formed through the transfer of electrons from one atom to another, resulting in the formation of positively and negatively charged ions. These ions are held together by strong electrostatic forces known as ionic bonds.
- Molecular Compounds: Formed through the sharing of electrons between atoms to form covalent bonds. Atoms in molecular compounds share electrons to achieve stable electron configurations without forming charged ions.
- Ionic Compounds: Composed of a three-dimensional array of positively and negatively charged ions arranged in a repeating pattern called a crystal lattice. These compounds do not exist as discrete molecules but rather as an extended network of ions.
- Molecular Compounds: Consist of discrete molecules, where atoms are held together by covalent bonds within each molecule. The molecules may be simple (e.g., H2O) or complex (e.g., proteins), but they exist as distinct entities.
- Physical Properties:
- Ionic Compounds: Generally have high melting and boiling points due to the strong electrostatic forces between ions in the crystal lattice. They are solid at room temperature and can conduct electricity when molten or dissolved in water (aqueous solution) due to the mobility of ions.
- Molecular Compounds: Often have lower melting and boiling points compared to ionic compounds due to weaker intermolecular forces between molecules. They can exist as solids, liquids, or gases at room temperature, depending on the strength of intermolecular forces. Molecular compounds do not conduct electricity in any state because they do not contain freely moving ions.
- Ionic Compounds: Many ionic compounds are soluble in polar solvents such as water because the polar water molecules can interact with and stabilize the charged ions, facilitating their dissolution.
- Molecular Compounds: Solubility varies widely depending on the polarity and intermolecular forces present in the compound. Polar molecular compounds tend to dissolve in polar solvents, while nonpolar molecular compounds dissolve in nonpolar solvents.
- Ionic Compounds: Examples include sodium chloride (NaCl), calcium carbonate (CaCO3), and magnesium oxide (MgO).
- Molecular Compounds: Examples include water (H2O), carbon dioxide (CO2), methane (CH4), and ammonia (NH3).
Last Updated : 10 February, 2024
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.