Electromagnetic Radiation and Energy

1
Electromagnetic Radiation and Energy

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

2
(No Transcript)
3
Electromagnetic Radiation and Energy

• c ? x ?
• c speed of light 2.9979 x 108 m/s
• ? frequency (s-1 or Hz)
• ? wavelength (m)

4
(No Transcript)
5
Spectra

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

6
Rydberg

• Why did gaseous atoms emit certain wavelengths?
• Didnt find out why, but came up with an equation
• Rydberg equation
• N3, red line
• N4, green line
• N5, blue line
• Lyman series
• n 1 to n 1
• UV (invisible)
• Balmer series
• n 2 to n 2
• Visible wavelengths

7
The Bohr Model of the Atom

• Explained Rydberg
• Electron energy quantized
• Electron only occupies certain energy levels or
  orbitals
• If it didnt, 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 (n1) to
  first excited state (n2)

8
Bohrs Model

• 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

9
Atomic orbital

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

10
The s-orbital

• 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

11
The p-orbitals

• Start in second principle energy level (n2)
• 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 theres
  zero probability of find an electron
• 2px 2py 2pz

12
The d-orbitals

• Start in third principle energy level (n3)
• 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
• 3dyz 3dxz
  3dxy 3dx2-y2
  3dz2

13
The f-orbitals

• Start in fourth principle energy level (n4)
• 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

14
Electron configuration

• Electron must be identified as to where it is
  located
• Hydrogen
• One electron in first energy level and s-subshell
• Thus, 1s1 ( Aufbau electron configuration)
• 1 states energy level (n)
• s designates subshell
• Superscript 1 tells how many electrons are in the
  s-subshell
• Can also use orbital box or line diagrams
• Lets take a look

15
Pauli Exclusion Principle

• An atomic orbital holds a maximum of two
  electrons
• Both electrons must have opposite spins
• ms 1/2 -1/2

16
Hunds Rule

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

17
Subshell filling order not what one expected
18
Using the Periodic Table to advantage
19
Short-hand vs. long-hand Aufbau electron
configuration

• F
• Al
• Ca
• Br

20
Exercises

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

21
Sundry matters pertaining to d-block metals

• Stability is increased when
• d-subshell is half-filled (d5)
• d-subshell is completely filled (d10)
• Electrons will be taken from the s-subshell to
  fill the d-subshell
• 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 d-subshell
• Ni Pt, for example

22
Sundry matters pertaining to f-block metals

• Stability is increased when
• f-subshell is half-filled (f7)
• f-subshell is completely filled (f14)
• Electron will be taken from the d-subshell to
  fill the f-subshell
• Eu Yb
• Am No