Ionic bonds transfer electrons from a metal to a nonmetal, making a cation and anion held by electrostatic attraction; covalent bonds share electrons between nonmetals. A large electronegativity gap gives ionic, a small gap gives covalent, and the in-between range gives polar covalent.
1. Ionic bonds transfer electrons from metal to nonmetal
A metal gives up electrons to a nonmetal, making a cation and an anion pulled together by electrostatic attraction.
2. Covalent bonds share electrons between nonmetals
Two nonmetals with similar electronegativity split the difference and share a pair of electrons instead of surrendering them.
3. Electronegativity difference is the dividing line
A large ΔEN gives ionic, a tiny ΔEN gives nonpolar covalent, and the middle range gives polar covalent bonds.
4. Polar covalent bonds carry partial charges
When sharing is unequal, the greedier atom turns δ− and its partner δ+ — a covalent bond with an ionic streak.
5. Organic chemistry is almost entirely covalent
Carbon sits mid-scale in electronegativity, so it shares rather than transfers — every C–C and C–H bond is covalent.
6. The bond type sets the physical properties
Ionic lattices are high-melting solids that conduct when dissolved; covalent molecules melt lower and stay non-conducting.
7. Summary
Ionic = electrons transferred (metal + nonmetal → cation + anion) · covalent = electrons shared (nonmetal + nonmetal) · ΔEN decides: large → ionic, small → nonpolar, in between → polar covalent · organic chemistry is covalent · ionic solids are high-melting conductors, covalent molecules melt lower.
Quiz yourself
Tap a question to reveal the answer — free, no login.
In NaCl the electron is fully transferred: sodium loses one to become Na⁺ and chlorine gains it to become Cl⁻, and the ions are held by electrostatic attraction. In ethane the C–C electrons are shared between the two carbons — no ions form.
A large ΔEN (metal + nonmetal, like NaCl) transfers electrons → ionic. A small ΔEN (like C–C or C–H) shares them evenly → nonpolar covalent. An intermediate ΔEN (like H–Cl) shares unequally → polar covalent, with δ+ and δ− partial charges.
Carbon's middle-of-the-road electronegativity means it neither donates nor fully grabs electrons — it shares them. Its bonds to hydrogen, other carbons, and most nonmetals are therefore covalent, so organic molecules are shared-electron networks, not ion lattices.
MgO is a rigid 3-D lattice of Mg²⁺ and O²⁻ ions, and breaking every strong electrostatic attraction takes enormous energy. Chloromethane is discrete covalent molecules held together only by weak intermolecular forces, so very little energy pulls them apart.
Draw this on the whiteboard
Open the OChem Board whiteboard — benzene rings, wedge/dash bonds, and a clickable periodic table built in. No account needed.