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 Shells

Take 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 FLUORINE, you already know that the atomic number tells you the number of electrons. That means there are 9 electrons in a fluorine atom. Looking at the picture, you can see there are two electrons in shell one and seven in shell two.

# Lithium Fluoride

One lithium (Li) atom can combine with one fluorine (F) atom. Together, they make the formula LiF. Fluorine has seven electrons of it's own. Lithium gives up its one electron to make both atoms happy. So the fluorine atom has eight electrons, and a filled outer shell.

# Beryllium Fluoride

Two fluorine (F) atoms can also bond with one beryllium (Be) atom, making the formula BeF2. Beryllium gives up one of it's electrons to each of the fluorine atoms. The result give each of the fluorines eight electrons, making their shells full.

# Aluminum Trifluoride

Fluorine (F) can also bond with aluminum (Al). Aluminum has three extra electrons and will easily let the fluorine atoms use them. Because aluminum has three, that means three fluorines can bond. The make the formula AlF3, also known as aluminum trifluoride. Each of the fluorine atoms gets an electron to fill their shell, and the aluminum loses three, giving it a filled shell too (remember, aluminum has three extra electrons). The name trifluoride means three fluorine atoms are involved.

- Chem4Kids: Periodic Table
- Chem4Kids: Atoms
- Chem4Kids: Compounds
- Chem4Kids: Halogens
- Chem4Kids: Chlorine
- Chem4Kids: Chemical Bonds