Formation of Covalent Bonds
Simple Explanation
A covalent bond forms when two atoms share one or more pairs of electrons, rather than fully transferring them. Each atom contributes electrons to a shared pair that effectively counts toward both atoms' octets at once.
Why Do We Need It?
Covalent bonding is how nonmetal atoms β which all want to gain electrons, so none of them can simply give electrons away β still manage to reach a stable octet, by sharing rather than transferring.
Why Does This Work?
When two atoms have similar (usually high) electronegativities, neither can pull electrons completely away from the other. Instead, both nuclei attract the same pair of electrons, and a stable bond forms where the shared electron pair sits between the two positively charged nuclei, attracted to both at once.
Real-Life Example
The oxygen you breathe
Oxygen gas in the air exists as Oβ molecules, not single oxygen atoms.
Each oxygen atom needs 2 more electrons for a full octet; two oxygen atoms share two pairs of electrons (a double bond) so that each atom effectively "sees" a full octet, without either atom fully gaining or losing electrons.
Practice
Two chlorine atoms bond to form Clβ. What kind of bond forms, and why?
MediumCommon mistake
Thinking only nonmetal-nonmetal pairs can bond covalently because 'nonmetals share' as a rule of thumb without understanding why β the real reason is that similar (typically high) electronegativities prevent either atom from pulling electrons away completely, which is what characterizes nonmetals in general.
Quick Review
- Covalent bonds form by sharing electron pairs, not transferring them.
- They typically form between atoms with similar, often high, electronegativity.
- The shared pair is attracted to both nuclei, holding the atoms together.