What Do They Look Like?
• Atoms are too small to see
with the unaided eye.
Electron Configuration
Unit Essential Question:
– Only way to see them is with a
special type of microscope
known as a scanning tunnel
microscope.
• Uses a beam of electrons.
What is the relationship between the physical and chemical properties of an element
and its atomic structure?
What is the purpose of the periodic table and why is it arranged the way it is?
Nickel Atoms
• To study atoms, we use models to describe how they
work and interact.
Presentation Objectives:
§ Explain that electrons can only be located in certain places because of their energy.
§ Explain that each energy level can only hold a certain number of electrons.
§ Demonstrate how to draw a Bohr Diagram and a Lewis Structure.
§ Define the term valence electron and explain how these electrons determine an
element’s behavior.
What is the Main Difference?
The Bohr Model
• In the Bohr model of the atom, these places are
known as energy levels or shells.
• Once the nucleus was
discovered by Rutherford, the
models only differed in the
electron configuration.
• Configuration means, where are
the electrons located.
Gold-foil experiment
• The newer models recognized that the electrons
cannot just be anywhere outside the nucleus.
• They can only be certain places based on their energy.
• The energy levels are represented as rings
around the nucleus.
Energy shells are labeled with a number beginning with 1!
Let’s Make It More…Interesting
• We cannot define an orbit for electrons like we do
with the planets around the sun.
– Heisenberg Uncertainty Principle
• Therefore, the most accepted model currently places
the electrons in an orbital.
– Region of space where the electron could be at
any given moment.
Bohr Model & Lewis Structures
• In this class, we utilize the Bohr model because it
can help us understand the basic behaviors of
atoms.
– You will learn more about orbitals when you get to
Chemistry.
• Another important representation of an atom is the
Lewis structure.
Let’s see how it all works!