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Energy Level Diagrams


Recall: The number of protons in the nucleus of an atom (the atomic number of an element).

Recall: The number of electrons around the nucleus of an atom (the number of protons).

    An energy level diagram represents the specific value of energy of an electron and corresponds to a general location. The number of occupied energy levels in any atom is normally the same as the period number in which the atom appears. For the first three energy levels, the maximum number of electrons that can be present are 2, 8, and 8, in order of increasing energy.  A lower energy level is filled with electrons to its maximum before the next level is started. The electrons in the highest energy level that contains any electrons are valence electrons. For the representative elements (1, 2, 12-18), the number of valence electrons is the same as the last digit of the group number of the atom.

Example: Bromine (Br) is found in group number 17. This means that Bromine (Br) has seven valence electrons.



               ^ The Symbols ^        


 
The markings that are found above are the symbols that are used when marking an energy level diagram. The symbol on the left is the first one you use, and the symbol on the right is the second one you use. The symbols must be used in this order, if they are not, then your energy level diagram is wrong. 

 

 

 When working on an energy level diagram, you must use the above chart. You begin with 1s, and continue on until you have the element's energy level diagram complete. Remember to follow the red arrows. This means that when you start from 1s, you continue on to 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on...
 

REMEMBER:
S holds 2 symbols
P holds 6 symbols
D holds 10 symbols
F holds 14 symbols 
 
If you are wondering what a energy level diagram looks like, you can see one that has already been completed below.