Ionic vs. Covalent Bonds: What's the Difference?

Atoms rarely exist alone — most of the matter around you is made of atoms bonded together into compounds. There are two main ways this bonding happens: ionic and covalent.

Ionic bonds: giving away electrons

An ionic bond forms when one atom transfers an electron (or more) to another atom entirely. This typically happens between a metal and a nonmetal:

• The metal loses one or more electrons, becoming a positively charged ion (a cation).
• The nonmetal gains those electrons, becoming a negatively charged ion (an anion).
• The opposite charges attract, holding the compound together.

Table salt is the classic example: sodium (Na) gives up one electron to become Na⁺, and chlorine (Cl) accepts it to become Cl⁻. The resulting NaCl is held together by the attraction between those two ions.

Covalent bonds: sharing electrons

A covalent bond forms when two atoms share electrons instead of transferring them outright. This typically happens between two nonmetals, since neither one is willing to fully give up an electron.

Water is the classic example: oxygen shares electrons with two hydrogen atoms. Neither atom fully owns those shared electrons — they're held in common, and that shared pair is what glues the atoms together.

A quick way to tell them apart

Try it yourself: browse the Ions table in Science Lab — every entry there is an ion formed by exactly this kind of electron transfer. Click one to see its actual electron count compared to the neutral atom.