Question: what are molecules?

Jimi Wills answered on 17 Mar 2016:

Molecules are collections of atoms joined together.

Atoms are things made of a nucleus and surrounding electrons.

When more than one nucleus gets together and start sharing some of their electrons, that’s a molecule.

For example, hydrogen gas is made of hydrogen atoms… but when it shares it’s electrons with oxygen, we get water, which is a molecule.

Atoms can also stick together by charge, and we call this a salt… for example common salt, sodium chloride, happens when the sodium gives one of its electrons to the chlorine. Electrons are negatively charged, so the chlorine becomes negative and the sodium becomes positive, and they stick together because opposites attract.

More complex molecules can be made, especially in biology. The building blocks of DNA are called nucleobases. On average each one has about 30 atoms in it, and they all join together to make a long DNA molecule with billions of atoms in it.