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Atomic Structure and the Periodic Table: Aufbau Principle, Electron Configurations, and Ion Formation

This chapter discusses the development of the periodic table by Meyer and Mendeleev, the Aufbau principle, electron configurations, and the formation of ions. It also covers the shorthand notation for electron configurations and exceptions to electron filling.

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Atomic Structure and the Periodic Table: Aufbau Principle, Electron Configurations, and Ion Formation

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  1. Chapter 7 Atomic Structure

  2. The Periodic Table • Developed independently by German Julius Lothar Meyer and Russian Dmitri Mendeleev (1870”s) • Didn’t know much about atom. • Put in columns by similar properties. • Predicted properties of missing elements.

  3. Aufbau Principle • Aufbau is German for building up • As the protons are added one by one, the electrons fill up hydrogen-like orbitals. • Fill up in order of energy

  4. 7p 7s 6p 6d 6s 6f 5p 5d 5f 5s 4p 4f 4s 4d Increasing energy 3p 3s 3d Orbitals available to a Hydrogen atom 2p 2s 1s

  5. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s With more electrons, repulsion changes the energy of the orbitals.

  6. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s He with 2 electrons

  7. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s

  8. Details • Valence electrons- the electrons in the outermost energy levels (not d). • Core electrons- the inner electrons • Hund’s Rule- The lowest energy configuration for an atom is the one have the maximum number of unpaired electrons in the orbital. • C 1s2 2s2 2p2

  9. Details • Elements in the same column have the same electron configuration. • Put in columns because of similar properties. • Similar properties because of electron configuration. • Noble gases have filled energy levels. • Transition metals are filling the d orbitals

  10. The Shorthand • Write the symbol of the noble gas before the element • Then the rest of the electrons. • Aluminum - full configuration • 1s22s22p63s23p1 • Ne is 1s22s22p6 • so Al is [Ne] 3s23p1

  11. The Shorthand Sn- 50 electrons The noble gas before it is Kr Takes care of 36 Next 5s2 Then 4d10 [ Kr ] 5s2 4d10 5p2 Finally 5p2 [ Kr ] 4d10 5s2 5p2

  12. Exceptions • Cr = [Ar] 4s1 3d5 • Mn = [Ar] 4s2 3d5 • Half filled orbitals • Scientists aren’t certain why it happens • same for Cu [Ar] 4s13d10

  13. Formation of Ions Metals ALWAYS gain electrons • Form cations (+) charge Nonmetals ALWAYS lose electrons • Form anions (-) Charge

  14. Formation of Ions Groups I and 2: Single ion formed is based on the number of “s” electrons Transition Metals: First Ion = # “s’ electrons Second = # “s” electrons + 1 P Sublevel Metals: First Ion = # “p” electrons Second Ion = # “p” + # “s” electrons

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