# How are covalent bonds formed?

Oct 3, 2016

By sharing electrons.

#### Explanation:

The simplest, hydrogen, has only one electron, but all atoms "want" their outer shell to be filled.
Now by sharing their electrons, in a way two $H$ atoms both have two electrons: This is denoted by:

$H : H$ or more usually

$H - H$ where $-$ stands for an electron- pair .

Oxygen, that lacks two electrons to make a full (8) shell looks like:

$O : : O$ or, more usually $O = O$ (a double bond)

Different atoms can also share electrons like:

$H - O - H$ (water) or $O = C = O$ (carbondioxide)