5.2 QUANTUM THEORY AND THE ATOMPART THREE

Quantum numbers and orbitals

Review: in Bohr’s atomic model, electrons orbited the nucleus as shown below. To mathematically describe the orbit of an electron, Bohr used one quantum number, n = 1, 2, 3 ……which designated 2 things:

The orbit for n = 1 isCLOSEST TO MOST FAR FROMthe nucleus, and isHIGHEST LOWESTin energyBohr’s orbits were all_____________________in shape.

In quantum theory, electrons may be found in atomic orbitals.The book says an orbital is:

“a 3-D region around the nucleus that describes the probable location of an electron.”

in other words:

each orbital can contain ____, ____, or ____ electrons (how many?)

Quantum mechanics has ______________ quantum numbers to describe the

arrangement of electrons. The first quantum number is known as the

and is very similar to Bohr’s. It is n = 1, 2, 3 ……

and describes roughly the same things as Bohr’s quantum number, n.

In quantum mechanics, the principal, the second, and the third quantum numbers together describe the

of an electron; i.e., the area of space that the electron has a________% probability of being found in;

The fourth quantum number describes a particular electron in that orbital (actually the spin of the electron.)

QUANTUM#

SPECIFIES DESCRIBES FOR AN ORBITAL…

Principal:quantum #n = 1, 2, 3….

Secondquantum #

Third Quantum#

Bohr’s orbits were all _____________ in shape.

In quantum mechanics, each orbital has one of

______________ different possible shapes.

A sublevel contains ______________________ orbitals, depending on the shape of the orbitals

All of the orbitals in a particular sublevel have

THE SAME DIFFERENT shape(s)

s orbitals are shaped like a sphere. How many orbitals can there be in

one s-sublevel?

p orbitals are shaped like a figure-8. There are 3 in any one p-sublevel.

Each one has a different orientation in space

d-orbitals are mostly shaped like 2 figure-8’s together. There are 5 of

them in any one d-sublevel.

Here are f orbitals. Any one sublevelcan contain 7 f orbitals

The orbitals have differing amounts of energy. For orbitals in the same principle energy level:

s < p < d < fLook at the shapes – does this make sense?

The Aufbau Principle states that:

each electron occupies the lowest energy orbital available.

Does this make sense?

With this basic knowledge of quantum numbers and orbitals, we can now begin to develop a picture of the atom and to write electron configurations; this is a very important skill in chemistry. Based on the electron configuration of each element, we can explain and predict the behavior of that element.