This is a basic water molecule. It is made up of three atoms: 2 atoms of Hydrogen (H) and 1 atom of Oxygen (O).
Atoms are collections of tiny particles which we call protons, neutrons, and electrons. They are not all mixed together, but follow a pattern. Think of the protons and neutrons as being in the center of an atom, and the electrons whizzing around the center in orbits. Kind of like planets orbiting around the sun. Kind of. The center of an atom is called the nucleus. The electrons orbit around the nucleus like how the planets orbit the sun. Scientists call these orbits “shells”.
For example, this is the Hydrogen atom:
The electron shells can only have a certain amount of electrons in them. If shells have empty spaces, they fill them in by sharing electrons from other atoms until the shell is full.
The inner shell, if full, has two electrons. The second shell, if full, has eight electrons. Here is how it looks:
tron shelSome atoms have outer elels that are not full. When an atom’s outer electron shell is completely full, it is stable and will not bond with other atoms. Atoms like to be stable, and will share electrons so they can fill their outer shell.
For example, look below at this atom, Oxygen (O). It has 2 electrons in its inner shell. So it is full. The second shell has room for 8 electrons, but Oxygen has only 6 electrons there. So it has room for 2 more electrons before it is full and stable.
So we can see Oxygen has 2 empty spots that could take electrons:
We already saw that a Hydrogen atom has 1 electron. Imagine an Oxygen atom, which has room for 2 extra electrons in its outer shell, met two Hydrogen atoms that could share their electrons.
You might end up with this:
How do we know this works?
- The Oxygen atom had 2 empty spaces in its outer shell. The 2 Hydrogen atoms fill those spaces with their two electrons.
- Each Hydrogen atom has space for 1 electron in its first (and only) shell. Each can share one of the electrons from the Oxygen atom.
- All 3 atoms are now stable. So they will stick together.