1. Diagramming Atoms Labeling Electrons – Part 1
Supplement to Book – Glencoe: Chapter 22 and 19-3

2. Electron shell diagrams
Electron shell diagrams are ways to visualize the arrangement of electrons in an atom
These diagrams
show which energy
levels, called shells,
the electrons are
found.

3. Electron shell diagrams
Particle locations
1. Nucleus
All protons (p+)
are found in
the nucleus
All neutrons (N)

4. Electron shell diagrams
2. Electron Cloud
- All electrons (e-)
are found in the
electron clouds
in orbitals

5. Electron shell diagrams
3. Neutral atoms of any element have equal numbers of protons and electrons
4. The number of neutrons can be found
from the atomic mass of an element
- Round atomic mass to the nearest whole number
 mass number
- Mass number = Atomic number + neutron number

6. Energy levels in atoms
1. Electrons are modeled in atoms combining two atomic models
- Bohr’s model – electrons orbit the nucleus in fixed paths
- The modern atomic model – electrons are found in areas called electron clouds

7. Energy levels in atoms
2. There are distinct energy levels in an atom  “n” number
a. “n” can equal
1, 2, 3, 4, 5, 6, or 7
b. Only whole, n = 1
non-negative
numbers
n = 2
n = 3

8. Energy levels in atoms
3. Energy level numbers generally correspond to period number (there is a pattern to it)

9. Energy levels in atoms 4. Each energy level may contain only a
specific maximum number of electrons
n # 1 2 3 4 5 6 7
Max e- 8 18 32

10. Energy levels in atoms Energy levels fill up in a specific order to
 lowest energy (n = 1) to
highest energy (n = 7)