Key Difference – Ionic vs Covalent Compounds
Many differences can be noted between ionic and covalent compounds based on their macroscopic properties such as solubility in water, electrical conductivity, melting points and boiling points. The main reason for these differences is the difference in their bonding pattern. Therefore, their bonding pattern can be deemed as the key difference between ionic and covalent compounds. (Difference Between Ionic and Covalent Bonds) When ionic bonds are formed, electron(s) is donated by a metal and donated electron(s) is accepted by a non-metal. They form a strong bond due to the electrostatic attraction. Covalent bonds are formed between two non-metals. In covalent bonding, two or more atoms share electrons to satisfy the octet rule. Generally, ionic bonds are stronger than covalent bonds. This leads to the differences in their physical properties.
What are Ionic Compounds?
Ionic bonds are formed when two atoms have a large difference in their electronegativity values. In the process of bond formation, the less electronegative atom losses electron(s) and more electronegative atom gains those electron(s). Therefore, resulting species are oppositely charged ions and they form a bond due to the strong electrostatic attraction.
Ionic bonds are formed between metals and non-metals. In general, metals do not have many valence electrons in the outermost shell; however, non-metals have closer to eight electrons in the valence shell. Therefore, non-metals tend to accept electrons to satisfy the octet rule.
Example of ionic compound is Na+ + Cl– à NaCl
Sodium(metal) has only one valence electron and Chlorine (non-metal) has seven valence electrons.
What are Covalent Compounds?
Covalent compounds are formed by sharing electrons between two or more atoms to satisfy the “octet rule”. This bonding type is commonly found in non-metal compounds, atoms of the same compound or nearby elements in the periodic table.Two atoms having nearly the same electronegativity values do not exchange (donate / receive) electrons from their valence shell. Instead, they share electrons to achieve octet configuration.
Examples of covalent compounds are Methane (CH4), Carbon monoxide (CO), Iodine monobromide (IBr)
Covalent Bonding
What is the difference between Ionic and Covalent Compounds?
Definition of Ionic Compounds and Covalent Compounds
Ionic compound: Ionic compound is a chemical compound of cations and anions which are held together by ionic bonds in a lattice structure.
Covalent compound: Covalent compound is a chemical bond formed by the sharing of one or more electrons, especially pairs of electrons, between atoms.
Properties of Ionic and Covalent Compounds
Physical Properties
Ionic Compounds:
All ionic compounds exist as solids at room temperature.
Ionic compounds have a stable crystal structure. Therefore, they have higher melting points and boiling points. The forces of attraction between positive and negative ions are very strong.
| Ionic Compound | Appearance | Melting Point |
| NaCl – Sodium chloride | White crystalline solid | 801°C |
| KCl – Potassium chloride | White or colourless vitreous crystal | 770°C |
| MgCl2– Magnesium chloride | White or colourless crystalline solid | 1412 °C |
Covalent Compounds:
Covalent compounds exist in all three forms; as solids, liquids and gases at room temperature.
Their melting and boiling points are relatively low compared to the ionic compounds.
| Covalent Compound | Appearance | Melting Point |
| HCl-Hydrogen chloride | A colourless gas | -114.2°C |
| CH4 -Methane | A colourless gas | -182°C |
| CCl4 – Carbon tetrachloride | A colourless liquid | -23°C |
Conductivity
Ionic Compounds: Solid ionic compounds do not have free electrons; therefore, they do not conduct electricity in solid form. But, when ionic compounds are dissolved in water, they make a solution which conducts electricity. In other words, aqueous solutions of ionic compounds are good electrical conductors.
Covalent Compounds: Neither pure covalent compounds nor dissolved forms in water do not conduct electricity. Therefore, covalent compounds are poor electrical conductors in all phases.
Solubility
Ionic Compounds: Most of the ionic compounds are soluble in water, but they are insoluble in non-polar solvents.
Covalent Compounds: Most of the covalent compounds are soluble in non-polar solvents, but not in water.
Hardness
Ionic Compounds: Ionic solids are harder and brittle compounds.
Covalent Compounds: Generally, covalent compounds are softer than ionic solids.
Image Courtesy:“Covalent bond hydrogen” by Jacek FH – Own work. (CC BY-SA 3.0) via Commons “IonicBondingRH11” by Rhannosh – Own work. (CC BY-SA 3.0) via Wikimedia Commons
