Check out the blackboard. That box on the left has all of the information you need to know about one element. It tells you the mass of one atom, how many pieces are inside, and where it should be placed on the periodic table.
In the next section we're going to cover electron orbitals or electron shells. This may be a new topic to some of you.
Electrons In The ShellsTake a look at the picture below. Each of those colored balls is an electron. In an atom, the electrons spin around the center, also called the nucleus. The electrons like to be in separate shells/orbitals. Shell number one can only hold 2 electrons, shell two can hold 8, and for the first eighteen elements shell three can hold a maximum of eight electrons. As you learn about elements with more than eighteen electrons you will find that shell three can hold more than eight. Once one shell is full, the next electron that is added has to move to the next shell.
So... for the element of HELIUM, you already know that the atomic number tells you the number of electrons. That means there are 2 electrons in a helium atom. Looking at the picture, you can see there are two electrons in shell one. That means the first shell is full.
Examples of Compounds with Helium
HeliumHelium (He) is the first of the Noble Gases. It is very non-reactive. So much so, that it doesn't form compounds with anything. Just like neon (Ne) and argon (Ar), helium just floats around all by itself.
It is non-reactive because it's shell is full. Helium only has one atomic shell, which fills up when it has two electrons.