• Quantum mechanics

– electrons can only exist in specified energy states

• Electron cloud model

– orbital: region around the nucleus where electrons are likely to be found

Erwin Schrodinger

Electron Cloud Model (orbital)• dots represent probability of finding an e-

not actual electrons

Erwin Schrodinger

Schrodinger’s Cat

http://www.youtube.com/watch?v=pNTMYNj2Ulk

• 1931• Finds mass of Proton

James Chadwick

•Irene Joliot Curie

• 1931• Finds Neutron

• 1951

• Transuranic Elements

Glen Seaborg

• Bohr was right about electrons moving around the nucleus

• Wrong about them moving like a planet in the solar system.

Electron Cloud Model

An electron cloud is the model that shows most likely where electrons are and their motions.

Heisenberg Uncertainty Principle◦ It is impossible to tell where an electron is at any

given moment.

It is similar to a plane propeller moving. You can’t really tell where the blade is exactly.

Electron Cloud

• Since we can’t know where an electron is, the probable location of an electron is based on how much energy the electron has.

• According to the modern atomic model, an atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make an atom neutral.

Electron Cloud Model

Electron Cloud• Electrons whirl about the

nucleus billions of times in one second

• They are not moving around in random patterns.

• Instead of energy levels as Bohr predicted, the electrons are found in an orbital region. The electron can be anywhere within that orbital, but it is impossible to know where it is.