Guides
Ionic vs Covalent Bonds — Differences, Table & How to Tell
Chemical bonds set many of a substance's properties. Ionic and covalent are the two most basic bond types: one works by giving and taking electrons, the other by sharing them. A quick way to tell them apart is the electronegativity difference between the bonded atoms.
Comparison table
| Aspect | Ionic bond | Covalent bond |
|---|---|---|
| Formation | electron transfer | electron sharing |
| Between | metal + nonmetal | nonmetal + nonmetal |
| Electronegativity diff. | large (often > 1.7) | small (< 1.7) |
| Examples | NaCl, MgO, CaF₂ | H₂O, CO₂, HCl, O₂ |
| Melting point | high | molecular solids usually low |
| Conductivity | conducts when molten or dissolved | usually non-conducting |
How to tell
Look at the electronegativity difference between the two elements: a large difference (metal with a reactive nonmetal) leans ionic; a small one (two nonmetals) leans covalent. A difference of zero (same nonmetal, e.g. O₂) is a pure covalent bond. Treat this as a trend, not a hard line.
More
- Covalent bonds are further split into polar (different nonmetals, e.g. HCl) and nonpolar (same element, e.g. Cl₂).
- For the deeper metal/nonmetal contrast, see metals vs nonmetals.
- Look up specific substances' bonding and properties in the compound library.