Prentice-Hall © 2007General Chemistry: Chapter 8Slide 1 of 50

Dr. MendenhallLecture 2

April 14, 2010

CHEMISTRYNinth

Edition GENERAL

Principles and Modern Applications

Petrucci • Harwood • Herring • Madura

Chapter 8: Electrons in Atoms

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 2 of 50

Objectives

1 Electromagnetic Radiation

2 Quantum Numbers and Electron Orbitals1 Know how orbital energies are modified when more

than one electron is present in an atom

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 3 of 50

8-1 Electromagnetic Radiation

Electric and magnetic fields propagate as waves through empty space or through a medium.

A wave transmits energy.

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 4 of 50

EM Radiation

Low

High

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 5 of 50

Frequency, Wavelength and Velocity

Frequency () in Hertz—Hz or s-1. Wavelength (λ) in meters—m.

◦ cm m nm pm

(10-2 m) (10-6 m) (10-9 m) (10-10 m) (10-12 m)

Velocity (c)—2.997925 108 m s-1.

c = λ λ = c/ = c/λ

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 6 of 50

Electromagnetic Spectrum

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 7 of 50

Refraction of Light

Slide 10 of 50 General Chemistry: Chapter 8 Prentice-Hall © 2007

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 8 of 50

9-2 Atomic Spectra

Slide 11 of 50 General Chemistry: Chapter 8 Prentice-Hall © 2007

(a) (b) (c) (d) (e)

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 9 of 50

Atomic Spectra

Helium

Hydrogen

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 10 of 50

8-3 Quantum Theory

Blackbody Radiation:

Max Planck, 1900

є = hEnergy, like matter, is discontinuous.

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 11 of 50

The Photoelectric Effect

Heinrich Hertz, 1888 Light striking the surface

of certain metals causes ejection of electrons.

> o

threshold frequency

#e- I ek

Albert Einstein 1905

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 12 of 50

The Photoelectric Effect

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 13 of 50

The Photoelectric Effect

At the stopping voltage the kinetic energy of the ejected electron has been converted to potential.

mu2 = eVs12

At frequencies greater than o:

Vs = k ( - o)

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 14 of 50

The Photoelectric Effect

Eo = hoEk = eVs o = eVo

h

eVo, and therefore o, are characteristic of the metal.

Conservation of energy requires that:

h = mu2 + eVo2

1

mu2 = h - eVo eVs = 2

1

Ephoton = Ek + Ebinding

Ek = Ephoton - Ebinding

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 15 of 50

Principle Shells and Subshells

Principle electronic shell, n = 1, 2, 3… Angular momentum quantum number,l = 0, 1, 2…(n-1)

l = 0, sl = 1, pl = 2, dl = 3, f

Magnetic quantum number, ml= - l …-2, -1, 0, 1, 2…+l

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 16 of 50

Orbital Energies

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 17 of 50

Relationship b/w quantum numbers & atomic orbitals

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 18 of 50

Orbital Energies

Degenerate orbitals: orbitals that have same energy

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 19 of 50

Orbital Filling

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 20 of 50

Electron Configurations

Aufbau process. Build up and minimize energy.

Pauli exclusion principle. No two electrons can have all four quantum

numbers alike.

Hund’s rule. Degenerate orbitals are occupied singly first.

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 21 of 50

Aufbau Process and Hunds Rule

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 22 of 50

Filling p Orbitals

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 23 of 50

Filling the d Orbitals

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 24 of 50

Prentice-Hall © 2007General Chemistry: Chapter 8Slide 25 of 50

8-12 Electron Configurations and the Periodic Table