INTRODUCTION TO BOHR MODELS
OBJECTIVE
 I can demonstrate the arrangement of sub-atomic particles and explain how these particles form elements.
 I can diagram the energy levels in an atom.
Niels Bohr suggested that the electrons moved around the nucleus in circular paths or orbits. After more research,
Schrödinger further stated that electrons do not have a specified path around the nucleus but reside in an electron cloud;
no pattern lines exist. The electrons found orbiting in this area are organized into energy levels or shells. There are 7
energy levels in the electron cloud (we will only be looking at the first three levels). In order for electrons to move from
one level to another, they must gain or lose energy. A quantum of energy is the amount of energy needed to move an
electron from its current level to the next higher level. Each level has a maximum number of electrons that it can hold.
The first orbit closest to the nucleus is called the first energy level, and it can hold a maximum of two electrons. You
must fill this level before moving out to the next energy level. The second energy holds 8, the third energy level can hold
up to eighteen electrons and the fourth energy level holds 32 electrons. The outermost energy level is referred to as the
valence energy level.
The atomic number (number of protons or number of electrons) of an element determines how many total electrons an
element will have in its energy levels. The group number of the element determines how many valence electrons
(electrons in the outermost shell) the element has.
1st Level – up to 2 electrons
2nd Level – up to 8 electrons
3rd Level – up to 18 electrons (8)
4th Level – up to 32 electrons
Steps to Solving Bohr Diagrams…
1. Find the atomic number of the element on the periodic table.
2. Draw the nucleus of the atom and write the atomic number in the center.
3. Determine the number of electrons for the atom.
4. Fill the first energy level and move to the next if needed.
Example : Lithium
Example : Magnesium
Atomic # _____________________
Mass # ______________________
Valence Electrons _____________
Atomic # _____________________
Mass # ______________________
Valence Electrons _____________