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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

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electromagnetic radiation and energy
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
electromagnetic radiation and energy3
Electromagnetic Radiation and Energy

c = λ x ν

c = speed of light = 2.9979 x 108 m/s

ν = frequency (s-1 or Hz)

λ = wavelength (m)

spectra
Spectra
  • Sunlight yields continuous spectrum
  • Energized gaseous elements yield certain wavelengths
    • Line emission spectrum
rydberg
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)
  • Balmer series
    • n > 2 to n = 2
      • Visible wavelengths
the bohr model of the atom
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)
bohr s model
Bohr’s 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
atomic orbital
Atomic orbital

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

the s orbital
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
the p orbitals
The p-orbitals
  • 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

2px 2py 2pz

the d orbitals
The d-orbitals
  • 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

3dyz 3dxz 3dxy 3dx2-y2 3dz2

the f orbitals
The f-orbitals
  • 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
electron configuration
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
        • Let’s take a look
pauli exclusion principle
Pauli Exclusion Principle
  • An atomic orbital holds a maximum of two electrons
  • Both electrons must have opposite spins
  • ms = +1/2 & -1/2
hund s rule
Hund’s Rule
  • Electron configuration most stable with electrons in half-filled orbitals before coupling
exercises
Exercises
  • Give me the Aufbau electron configurations for:
    • Y
    • Te
    • Hf
    • Tl
    • 112
sundry matters pertaining to d block metals
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
sundry matters pertaining to f block metals
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