Question

Question #01d4a

Answer 1

Long ago, the covalent bond was explained to me by the polar bear analogy.

Two polar bears both have a bald piece of skin. As long as they keep the bald patch of the one against the bald patch of the other, they both stay warm.

Now translated: All atoms 'want' to have a filled outer electron shell. They can do this in two ways: (1) they can borrow an electron from an atom that has one too many, or (2) they can share an electron, and 'believe' it's theirs (at least part of the time).

The latter is called a covalent bond, because both atoms have (more or less) the same share of the electron(s).

Hydrogen `H` has one electron, but if it meets another `H` atom, they can share their two electrons and 'pretend' they are like helium (which has a full outer electron shell).

Now `H_2` is not a compound, because both atoms are the same (so it is an element), but let's look at water.

Oxygen `O` actually needs two extra electrons to fill its outer shell. It can share with another `O` to form `O_2` or with two `H`'s (and with other atoms, to form oxides).

The shared electron pair is called a bond, and is usually designated by a dash, like in water

`H:O:H hArrH-O-H`

Almost all organic compounds are based on bonds like this, and are thus called covalent compounds.