by Steven S. Zumdahl & Donald J. DeCoste University of Illinois Introductory Chemistry: A Foundation, 6 th Ed. Introductory Chemistry, 6 th Ed. Basic Chemistry, 6 th Ed.

Chapter 11 Modern Atomic Theory

Rutherford’s Atom Section 11-1

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 4 Rutherford’s Atom The concept of a nuclear atom (charged electrons moving around the nucleus) resulted from Ernest Rutherford’s experiments. Question left unanswered: how are electrons arranged and how do they move?

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 5 Rutherford’s Atom (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 6 Section 11-2 Electromagnetic Radiation

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 7 Electromagnetic Radiation (cont.) Electromagnetic radiation is given off by atoms when they have been excited by any form of energy, as shown in flame tests.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 8 Electromagnetic Waves Velocity = c = speed of light – x 10 8 m/s –All types of light energy travel at the same speed. Amplitude = A = measure of the intensity of the wave, i.e.“brightness”

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 9 Electromagnetic Waves (cont.) Wavelength =  = distance between two consecutive peaks or troughs in a wave –Generally measured in nanometers (1 nm = m) –Same distance for troughs Frequency = = the number of waves that pass a point in space in one second –Generally measured in Hertz (Hz), –1 Hz = 1 wave/sec = 1 sec -1 c = x

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 10 Types of Electromagnetic Radiation

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 11 Planck’s Revelation Showed that for certain applications light energy could be thought of as particles or photons

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 12 Planck’s Revelation (cont.) The energy of the photon is directly proportional to the frequency of light.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 13 Problems with Rutherford’s Nuclear Model of the Atom Electrons are moving charged particles. Moving charged particles give off energy; therefore the atom should constantly be giving off energy. The electrons should crash into the nucleus, and the atom should collapse!!

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 14 Section 11-3 Emission of Energy by Atoms

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 15 Emission of Energy by Atoms/Atomic Spectra Atoms that have gained extra energy release that energy in the form of light.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 16 Section 11-4 The Energy Levels of Hydrogen

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 17 Atomic Spectra Line spectrum: very specific wavelengths of light that atoms give off or gain Each element has its own line spectrum, which can be used to identify that element.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 18 Atomic Spectra (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 19 Atomic Spectra (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 20 Atomic Spectra (cont.) The atom is quantized, i.e. only certain energies are allowed.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 21 Section 11-5 The Bohr Model of the Atom

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 22 Bohr’s Model Explained spectrum of hydrogen Energy of atom is related to the distance of electron from the nucleus

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 23 Bohr’s Model (cont.) Energy of the atom is quantized –Atom can only have certain specific energy states called quantum levels or energy levels. –When atom gains energy, electron “moves” to a higher quantum level –When atom loses energy, electron “moves” to a lower energy level –Lines in spectrum correspond to the difference in energy between levels

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 24 Bohr’s Model (cont.) Ground state: minimum energy of an atom –Therefore electrons do not crash into the nucleus The ground state of hydrogen corresponds to having its one electron in the n=1 level Excited states: energy levels higher than the ground state

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 25 Bohr’s Model (cont.) Distances between energy levels decrease as the energy increases –1st energy level can hold 2e -1, the 2nd 8e -1, the 3rd 18e -1, etc. –Further from nucleus = more space = less repulsion Valence shell: the highest-energy occupied ground state orbit

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 26 Section 11-7 The Hydrogen Orbitals

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 27 Problems with the Bohr Model Only explains hydrogen atom spectrum (and other 1-electron systems) Neglects interactions between electrons Assumes circular or elliptical orbits for electrons (which is not true)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 28 Wave Mechanical Model of the Atom (cont.) The quantum mechanical model treats electrons as waves and uses wave mathematics to calculate probability densities of finding the electron in a particular region in the atom –Schrödinger Wave Equation –Can only be solved for simple systems, but approximated for others

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 29 Orbitals and Energy Levels Solutions to the wave equation give regions in space of high probability for finding the electron. These are called orbitals. Each principal energy level contains one or more sublevels. Sublevels are made up of orbitals.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 30 Orbitals and Energy Levels (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 31 Atomic Sublevels & Orbitals Each type of sublevel has a different shape each and energy. Each sublevel contains one or more orbitals.

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 32 Wave Mechanical Model of the Atom Experiments later showed that electrons could be treated as waves –Just as light energy could be treated as particles –De Broglie

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 33 Atomic Sublevels & Orbitals (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 34 Section 11-8 The Wave Mechanical Model: Further Development

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 35 Pauli Exclusion Principle No orbital may have more than 2 electrons. Electrons in the same orbital must have opposite spins. s sublevel holds 2 electrons (1 orbital) p sublevel holds 6 electrons (3 orbitals) d sublevel holds 10 electrons (5 orbitals) f sublevel holds 14 electrons (7 orbitals)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 36 Section 11-9 Electron Arrangements in the First Eighteen Atoms on the Periodic Table

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 37 For a multiple-electron atom, build-up the energy levels, filling each orbital in succession by energy Degenerate orbitals: orbitals with the same energy –e.g. Each p sublevel has 3 degenerate p orbitals Orbitals, Sublevels & Electrons

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 38 Orbitals, Sublevels & Electrons (cont.)

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 39 Electron Configurations For a set of degenerate orbitals, fill each orbital half- way first before pairing Electron configurations show how many electrons are in each sublevel of an atom – describes where electrons are. - 1s 2 2s 1 is the electron configuration for a ground state Li - 1s 2 2s 2 2p 3 is for nitrogen

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 40 Electron Configurations (cont.) Valence shell: highest energy level –Electrons in the valence shell are called valence electrons. –Core electrons: electrons not in the valence shell –Often use symbol of previous noble gas in brackets to represent core electrons, giving [He]2s 2 2p 3 for nitrogen or [Ne]3s 2 for magnesium

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 41 Section Electron Configurations and the Periodic Table

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 42 Electron Configuration and the Periodic Table Elements in the same column on the periodic table have: –Similar chemical and physical properties –Similar valence shell electron configurations same numbers of valence electrons same orbital types different energy levels

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 43 s1s1 s2s2 d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9 d 10 p 1 p 2 p 3 p 4 p 5 s2s2 p6p6 f 1 f 2 f 3 f 4 f 5 f 6 f 7 f 8 f 9 f 10 f 11 f 12 f 13 f

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 44

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 45 Section Atomic Properties and the Periodic Table

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 46 Metallic Character: Metals Metals –Malleable & ductile –Shiny, lustrous –Conduct heat and electricity –Most oxides basic and ionic –Form cations in solution –Lose electrons in reactions - oxidized

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 47 Metallic Character: Metalloids Metalloids -Also known as semi-metals -Show some metal and some nonmetal properties

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 48 Metallic Character: Nonmetals Nonmetals -Brittle in solid state -Dull -Electrical and thermal insulators -Most oxides are acidic and molecular -Form anions and polyatomic anions -Gain electrons in reactions - reduced

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 49 Metallic Character

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 50 Metallic Character (cont.) Reactivity of metals increases to the left on the period and down in the column –Follows ease of losing an electron Reactivity of nonmetals (excluding the noble gases) increases to the right on the period and up in the column

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 51 Trend in Ionization Energy Minimum energy needed to remove a valence electron from an atom –Gas state The lower the ionization energy, the easier it is to remove the electron. –Metals have low ionization energies Ionization energy decreases down the group. –Valence electron farther from nucleus Ionization energy increases across the period. –Left to right

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 52 Trend in Atomic Size

Copyright © Houghton Mifflin Company. All rights reserved. 11 | 53 Trend in Atomic Size (cont.)