Why Do Atoms and Molecules Stick Together?
-Learning the Skill of Making Bohr ModelsProtons (+) and neutrons (neutral) are found in the nucleus of an atom and do not generally move. If they do you would see a
nuclear reaction like the heat of a power plant or a nuclear weapon.
Most reactions you see around you on a daily basis occur because of the movement of electrons (-). You already know that electrons go around an
atom. Now consider that there are layers or “shells” around an atom. Each shell can only hold up to a certain number of electrons. If the atom has
fewer than this number in a shell then the atom will bind with other atoms to fill its shells. By sharing electrons atoms join together to form molecules
or chemical compounds. In the examples below the smallest shell can only hold up to 2 electrons. The next shell can hold up to 8 electrons and the
third shell can also hold up to 8 electrons. Remember that the number of electrons an atom has is equal to the number of protons an atom has (atomic
number). Follow Mr. Uhlman’s examples on the board then complete the rest of the worksheet.
Example:
Period
Boron
Hydrogen
Helium
1
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
2
3
Mr. Uhlman Science Fall 2015