Chem 101: SWIC-RBC

Dr. Clerc

 

Modern Atomic Theory – Ch. 5 Notes

 

(1) Solutions to wave equation predict the structure (periodicity) observed in the periodic table

 

                               “Pictures” of the atomic orbitals (click to view)

n=1: 1s

n=2: 2s, 2p

n=3: 3s, 3p, 3d

n=4: 4s, 4p, 4d, 4f

n=5: 5s, 5p, 5d, 5f, 5g  

 

                                       Note: n = row numbers of periodic table

 

Electron occupies energy “states” defined by three parameters:

            (1) principal quantum number: n

            (2) azimuthal quantum number: l

            (3) spin quantum number: m

 

   Each value of “n” corresponds to a different “shell” of orbitals (see p. 126).

   Each value of “l” corresponds to a different “subshell” (orbital type):

                  s (2 electrons), p (6 electrons), d (10 electrons), f (14 electrons), … .

   Example: the “p” subshell” contains three “p” orbitals which can accommodate 6 electrons

   Each value of m corresponds to a different “spin” (“up” or “down”)

 

(2)  Aufbau principle: Electrons fill lowest-energy orbitals first.

 

QuickTime videos of orbital-filling.

http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/aufbau-principle.html

 

Atomic Number

Element

1s

2s

2px

2py

2pz

3s

1

H

­

 

 

 

 

 

2

He

­¯

 

 

 

 

 

3

Li

­¯

­

 

 

 

 

4

Be

­¯

­¯

 

 

 

 

5

B

­¯

­¯

­

 

 

 

6

C

­¯

­¯

­

­

 

 

7

N

­¯

­¯

­

­

­

 

8

O

­¯

­¯

­¯

­

­

 

(3)   Transitions of electrons between orbitals: accompanied by absorption or emission of light. http://hyperphysics.phy-astr.gsu.edu/hbase/hyde.html#c4

 

 

(4)   Orbitals represent Probability Density (not actual location) of electron: See shapes on 126 (s), 127 top (p), 127 bottom (d).

 

 

(5)   Order of orbital-filling follows energy of orbitals: Compare Fig. 5-14 to Fig. 5-16 (below)

 

 

(6)  Electron Configuration (5-4) and Orbital Diagrams (5-5):

 

Pauli exclusion principle:  No two electrons in an atom can have identical quantum numbers. In other words, they cannot occupy the same orbital with the same spin.

 

Hund’s rules:  Electrons occupy separate orbitals in the same subshell with parallel spins.

Nobel-gas notation:  Shorthand method for writing configuration.

 

(7)  Interactive periodic tables (posted on class web site):  

            These demonstrate electron configuration.

 

(8)  Trends in the periodic table:

 

Ionization energy (p. 140): Energy required to remove an electron from a gaseous atom to form a gaseous ion.

 

Atomic radius (p. 140): Distance from the nucleus to the outermost electrons.

        

 

        

         The trends are: