•
Electromagnetic Radiation:
–
Energy traveling through space
Three Characteristics of Waves:
1.
Wavelength: (symbolized l)
1. Distance between two consecutive peaks or troughs in a wave
2.
Frequency: (symbolized n)
1. How many waves pass a given point per second
3.
Speed: (symbolized c)
1. How fast a given peak moves through space
1

2

c = λ x ν c = speed of light = 2.9979 x 10 8 m/s
ν = frequency (s -1 or Hz)
λ = wavelength (m)
3

4

Spectra
•
Sunlight yields continuous spectrum
•
Energized gaseous elements yield certain wavelengths
– Line emission spectrum
5

Rydberg
•
Why did gaseous atoms emit certain wavelengths?
– Didn’t find out why, but came up with an equation
•
Rydberg equation
– N=3, red line
– N=4, green line
– N=5, blue line
•
Lyman series
– n > 1 to n = 1
•
UV (invisible)
1 l
R (
2
1
2
 n
1
2
•
Balmer series
– n > 2 to n = 2
•
Visible wavelengths

-1
6

The Bohr Model of the Atom
•
Explained Rydberg
•
Electron energy quantized
– Electron only occupies certain energy levels or orbitals
• If it didn’t, electron would crash into protons in nucleus
• As “n” increases energy becomes less negative
– Increases
•
Only certain amts of E may be absorbed/emitted
• If electron in lowest possible energy level
–
Ground state
•
If electron in excited energy level
– Excited state
•
One can calculate energy needed to raise H electron per atom from ground state (n=1) to first excited state (n=2)

E = E - E = () ( f i
Rhc
2 2
 
Rhc
; J/atom n 2
Rhc
)

984kJ/mol
1 2
7

•
Explains emission spectrum of H
– Movement of electrons from one quantized energy level to a lower one gave distinct emission wavelengths
•
Model only good for one electron system
8

The probability function that defines the distribution of electron density in space around the atomic nucleus.
9

• The simplest orbital
•
The only orbital in the s-subshell
•
Occurs in every principal energy level
• “s” stands for “sharp”
• The first energy level only houses this orbital
• Can house up to 2 electrons
10

•
Start in second principle energy level (n=2)
•
There are three p-orbitals in the p-subshell (see below)
– And one s-orbital
• “p” stands for “principle”
• Can house up to 6 electrons
• Has one nodal surface
– Nodal plane = a planar surface in which there’s zero probability of find an electron
2p x
2p y
2p z
11

• Start in third principle energy level (n=3)
•
There are five d-orbitals in the d-subshell
– And one s-orbital
– And three p-orbitals
•
Can house up to 10 electrons
• “d” stands for “diffuse”
•
Has two nodal surfaces
3d yz
3d xz
3d xy
3d x 2 -y 2
3d z 2
12

•
Start in fourth principle energy level (n=4)
•
There are seven f-orbitals in the f-subshell
– And one s-orbital
– And three p-orbitals
– And five d-orbitals
•
Can house up to 14 electrons
• “f” stands for “fundamental”
•
Has 3 nodal surfaces
13

• Electron must be identified as to where it is located
– Hydrogen:
• One electron in first energy level and s-subshell
– Thus, 1s 1 (= Aufbau electron configuration)
• 1 states energy level (n)
• s designates subshell
• Superscript 1 tells how many electrons are in the ssubshell
• Can also use orbital box or line diagrams
– Let’s take a look
14

•
An atomic orbital holds a maximum of two electrons
• Both electrons must have opposite spins
• m s
= +1/2 & -1/2
15

•
Electron configuration most stable with electrons in half-filled orbitals before coupling
16

17

18

•
F
•
Al
•
Ca
•
Br
19

•
Give me the Aufbau electron configurations for:
– Y
– Te
– Hf
– Tl
– 112
20

•
Stability is increased when:
– d-subshell is half-filled (d 5 )
– d-subshell is completely filled (d 10 )
• Electrons will be taken from the s-subshell to fill the dsubshell
– But there is a limit
• No more than 2 electrons taken from s-subshell
• Given the above, which subshell electrons will d-block metals lose first when they ionize?
• So what are the correct electron configurations of Cr and Ag?
• Caveat
– Not all metals follow the above; i.e., take from s-subshell and give to dsubshell
•
Ni & Pt, for example
21

•
Stability is increased when:
– f-subshell is half-filled (f 7 )
– f-subshell is completely filled (f 14 )
•
Electron will be taken from the d-subshell to fill the f-subshell
– Eu & Yb
– Am & No
22