Docstoc

The Quantum Model

Document Sample
The Quantum Model Powered By Docstoc
					 Quantum Mechanics

A way to describe electron behavior
The Electromagnetic Spectrum




  V   I    B   G   Y   O   R

          …describes the wave nature of light
         All electromagnetic waves
    can be described by the equation:

                  c=f
           c = speed of light = 3.0 x 108 m/s
 (wavelength) is inversely proportional to f (frequency)

          As wavelength increases,
             frequency decreases
                  Wave Comparison
  Red Light
                                 nm = 1 x 10-9 m
• Low frequency
• Long wavelength


  Violet Light
• High frequency
•Short wavelength




                      emission
        Electron Energy as a Wave
• All of our understanding of electrons comes
  from radiant energy (light) they emit.
• All light can be described as
                particles (photons)
                      or as

 waves (electromagnetic radiation)
                   Max Planck
  studied the wavelengths of emitted by electrons…

and related their frequency to the energy difference between
shells.
                      E = hf
   (Energy difference) = (Planck’s constant) x (frequency)



                                      E
The electrons lose (release) energy
…and they fall back to their ground state;
the lost energy takes the form of light,
which we study.
              Spectral Lines
      When electrons “jump” from a higher
shell to a lower shell, they emit light.
     All of the “jumps” that occur in an
atom of on element result in a signature

    EMISSION SPECTRUM.
…for that element. Below is Mercury’s spectrum:
“Where” are the electrons?

 Like Bohr said,

electrons are found in shells…(“energy levels”)
 …but all shells contain subshells…

    …all subshells contain orbitals…

 …and every orbital contains two electrons.
to make a long story short…
       Niels Bohr
     Albert Einstein
   Werner Heisenberg
    Wolfgang Pauli     …described
    Louis de Broglie     electrons’
      Max Planck       location and
   Erwin Schrödinger    behavior by
      and others…       developing:
     Quantum Mechanical Theory
         “the new physics”
              Schrodinger
                   proposed
       4 Quantum Numbers
     to describe the location of an electron


n        the Primary Quantum Number

l        the Secondary Quantum Number
m1       the Magnetic Quantum Number
ms       the Spin Quantum Number
  n        the Primary Quantum Number

• the energy level (shell) of the electron.
• the average distance from the nucleus.
• n can be 1 through 7 .
• there can only be 2n2 electrons in a shell.
l    the Secondary Quantum Number

• the subshell (“sublevel”) of the electron
• each shell has n subshells.
• Names of subshells:
          s     (l = 0)
          p     (l = 1)
          d     (l = 2)
          f     (l = 3)
“Where” are the electrons?

 Like Bohr said,

electrons are found in shells…(“energy levels”)
 …but all shells contain subshells…

    …all subshells contain orbitals…

 …and every orbital contains two electrons.
m1 the Magnetic Quantum Number
• tells you which orbital the electron is in.
• each orbital has a specific shape.
• Shapes correspond to probability of
  finding an electron in that area.
• each orbital can hold 2 electrons.
 each subshell has a different number of orbitals!

                       There is only one orbital
                       in an s subshell.
                     s orbitals are spherical.
    orbitals of the p subshell:
• only start at the second shell (n=2)
• there are 3 orbitals in the p subshell.
• they have different orientations




 px orbital          py orbital        pz orbital
          m1 = -1             m1 = 0           m1 = +1
  orbitals of the d subshell:
• only start at the
  third shell (n=3)
• there are 5
  orbitals in the d
  subshell.
  orbitals of the f subshell:
• only start at
  the fourth
  shell (n=4)
• there are 7
  orbitals in the
  f subshell.
“Where” are the electrons?

 Like Bohr said,

electrons are found in shells…(“energy levels”)
 …but all shells contain subshells…

    …all subshells contain orbitals…

 …and every orbital contains two electrons.
 ms    the Spin Quantum Number



• the last quantum number describes spin
• Remember; only 2 e- per orbital
• the 2 electrons in an orbital will always
  have opposite spins.


ms ( “spin” ) can only be +   ½ or – ½
How many electrons in each
       subshell?

 Well, there are only 2 electrons
 allowed per orbital, so:
  •   s=   1 orbital     2 e-
  •   p=   3 orbitals    6 e-
  •   d=   5 orbitals    10 e-
  •   f=   7 orbitals    14 e-
             Summary
    # of     Max         Starts at
    orbitals electrons   energy level
s    1          2            1

p    3          6            2

d    5          10           3

f    7          14           4
 Remember…
Each shell has n subshells;
So…
the n = 1 shell only has one subshell:
    (an “s”)
the n = 2 shell has two subshells:
    (an “s” and a “p”)
the n = 3 shell has three subshells:
    (an “s” and a “p” and a “d")
                 Electron Diagrams
Each arrow represents an electron.
       Arrow direction indicates spin.

             Fill from the inside out, just like Bohr Model diagrams

Example: Cr


                                                       3d
                              3p         4s
                         3s
            2p
      2s
1s                                            “Hund’s Rule”;
                                               one e- in each
 Cr        1s22s22p63s23p64s23d4                orbital before
                                                   pairing
 Cr        [Ar] 4s23d4
 Writing Electron Configurations:



               2p4
Energy Level                        Number of
     n                              electrons in
                 Subshell          that subshell
               (s, p, d or f)

 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
 6s2 4f14… etc.
Some subshells
   overlap:




 So, we fill in this
      order:

1s2   2s2 2p6 3s2 3p6 4s2 3d10 4p6   5s2   4d10
             Orbitals and the
              Periodic Table
s orbitals
               d orbitals
                                p orbitals




  f orbitals
The secret of periodicity:
                         7p        6d
                    7s   6p                      5f
                                   5d
                    6s   5p                      4f
                                   4d
                    5s
Increasing energy



                         4p
                    4s             3d
                         3p
                    3s        Electron Configuration
                         2p     Diagram for Phosphorous
                    2s

                    1s
Fill from the bottom up following
            the arrows
7s 7p 7d 7f
6s 6p 6d 6f
               •   1s 2 2s2 2p6 3s2
5s 5p 5d 5f
                   3p 6 4s2 3d10 4p6
4s 4p 4d 4f
                   5s2 4d10 5p6 6s2
3s 3p 3d
                   4f14 5d10 6p6 7s2
2s 2p
                   5f14 6d10 7p6
1s
                • 108 electrons
         Let’s Try It!
• Write the electron configuration for
  the following elements:
   He
   Li
   N
   Ne
   K
   Zn
               Shorthand
• Chlorine
                Notation
  Longhand is
    1s2 2s2 2p6 3s2 3p5
  You can abbreviate the first
    10 electrons with [Ne]
    (replaces 1s2 2s2 2p6 )
  The next energy level after
    Neon is 3
  So you start at level 3 and
    finish by adding 7 more      [Ne]   3s 2   3p 5
    electrons to bring the
    total to 17
         Shorthand
          Notation
• Step 1: Find the closest noble gas to
  the atom (or ion), WITHOUT GOING
  OVER the number of electrons in the
  atom (or ion). Write the noble gas in
  brackets [ ].
• Step 2: Find where to resume by finding
     the next energy level.
• Step 3: Resume the configuration
    until it’s finished.
Practice Shorthand Notation
• Write the shorthand notation for each of the
  following atoms:
Cl
K
Ca
I
Bi

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:5
posted:6/21/2012
language:English
pages:36