Quantum Atom

Problem

Bohr model of the atom only successfully predicted the behavior of hydrogen

Good start, but needed refinement

Heisenberg Uncertainty Principle

It is not possible to know both the position and momentum (mv) of an electron

Cannot assume that the electron is moving around the nucleus in a well-defined orbit as in the Bohr model

Louis de BroglieSuggested matter that is assumed to be of a particle nature, does have wavelike properties

Developed an equation for actually calculating this wavelength of matter

For very small particles, wavelength is significant

h

mv

Wave Function

Erwin Schrodinger developed a series of equations that describe the areas of probability of finding an electron

There are different values of these wave functions that occur at different energy levels

Wave function are called Orbitals

Quantum Mechanics

Describes mathematically the properties of an electronShows regions of probability of finding an electron

Quantum Numbers

Principal Quantum Number (n) – same as the Bohr energy levelAlso called shellsRange from n=1 to n=7

Subshell or Sublevel

Angular Momentum Number

Come in four typess subshell (spherical)p subshell (dumbbell)d subshell (four lobes) f subshell

Orbital

Magnetic Quantum Number These are the orbitals (hold 2 e- each)Each sublevel may have more that one

orbital with a different orientation in spaces ( 1 orbital) p ( 3 orbitals) d (5 orbitals) f (7 orbitals)

Main Level Sublevels Number of orbitals

Electrons in sublevels

Total Electrons in Main Level

1 s 1 2 2

2 sp

13

26

8

3 spd

135

26

1018

4 spdf

1357

26

1014

32

Degenerate Orbitals

Orbitals that have the same energies

Electron Spin Number

Electron behaves as if it is spinning on its axis

Fourth Quantum number is the spin number

Spinning electrons produce magnetic fields

Pauli Exclusion Principle

No two electrons can have the same set of four quantum numbers

If an orbital has two electrons in it, they must have different spins

Electrons in the same orbital with different spins are called paired electrons

Configuration

Arrangement of electrons in the atom

Aufbau Principle – orbitals fill in order of increasing energy

Orbital Diagram of Li ( 3 e-)

1s22s1

Orbital Diagram of B (5 e-)

1s22s22p1

Hund’s Rule

Electrons occupy degenerate orbitals singly first

Orbital Diagram of C (6 e-)

1s22s22p2

Orbital Diagram of Ne (10 e-)

Configuration 1s22s22p6

Example

Determine the configuration of

Fe

Br

Magnetism

When electrons in half-filled degenerate orbitals spin in the same direction, the material is magnetic

Valence Electrons

Outer shell electrons

Ones in the last main energy level

▪ K 1s22s22p63s23p64s1 1 valence e

• Fe 1s22s22p63s23p64s23d6 2 valence e