Solutions to Electron Configurations Homework Set

1. Write the electron configuration (ie: 1s², 2s¹), orbital energy diagram, and orbital box diagram for,
   1. H, Li, Na, and K

      Element	Configuration	Short
      H	1s1	1s1
      Li	1s2, 2s1	[He] 2s1
      Na	1s2, 2s2, 2p6, 3s1	[Ne] 3s1
      K	1s2, 2s2, 2p6, 3s2, 3p6, 4s1	[Ar] 4s1

      I am unable to create box diagrams or energy level diagrams (without great effort) on the computer so you will have to look in your textbook for examples of thes. See page 373 in Kotz & Treichel for an example of the box diagram, and page 365 in Kotz & Treichel for an example of the energy level diagram (Fill this in with the arrows for the electrons).

   2. Be, Mg and Ca

      Element	Configuration	Short
      Be	1s2, 2s2	[He] 2s2
      Mg	1s2, 2s2, 2p6, 3s2	[Ne] 3s2
      Ca	1s2, 2s2, 2p6, 3s2, 3p6, 4s2	[Ar] 4s2

   3. C, Si and Ge

      Element	Configuration	Short
      C	1s2, 2s2, 2p2	[He] 2s2, 2p2
      Si	1s2, 2s2, 2p6, 3s2, 3p2	[Ne] 3s2, 3p2
      Ge	1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p2	[Ar] 4s2, 3d10, 4p2

   4. F, Cl and Br

      Element	Configuration	Short
      F	1s2, 2s2, 2p5	[He] 2s2, 2p5
      Cl	1s2, 2s2, 2p6, 3s2, 3p5	[Ne] 3s2, 3p5
      Br	1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p5	[Ar] 4s2, 3d10, 4p5

   5. Fe, Ni and Zn

      Element	Configuration	Short
      Fe	1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6	[Ar] 4s2, 3d6
      Ni	1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d8	[Ar] 4s2, 3d8
      Zn	1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10	[Ar] 4s2, 3d10

   6. Cl^1- and K¹⁺

      Element	Configuration	Short
      Cl1-	1s2, 2s2, 2p6, 3s2, 3p6	[Ne] 3s2, 3p6	[Ar]
      K1+	1s2, 2s2, 2p6, 3s2, 3p6	[Ne] 3s2, 3p6	[Ar]

   7. Mg²⁺ and F^1-

      Element	Configuration	Short
      Mg2+	1s2, 2s2, 2p6	[He] 2s2, 2p6	[Ne]
      F1-	1s2, 2s2, 2p6	[He] 2s2, 2p6	[Ne]

2. Use a blank periodic table and write in the periodic trends for,
   1. atomic size.
      • Larger as you go down and to the left. Cs is very large.
      • Smaller as you go up and right. He is very small.

   2. ionization energy
      • Increases as you go up and to the right. It is VERY difficult to take an electron from He.
      • Decreases as you go down and left. It is VERY easy to take ana electron from Cs.

   3. electron affinity
      • Increases as you go up and to the right. It is VERY easy to add an electron to F. (NOTE: Nobel gases are very difficult to add an electron to).
      • Decreases as you go down and left. It is VERY difficult to add an electron to Cs.

   4. ion size Here it is important to distinguish between posative ions and negative ions. Generally negative ions are larger than posative ions. For each type of ion:
      • Larger as you go down and to the left. Cs¹⁺ is a very large posative ion and Te^2- is a very large negative ion.
      • Smaller as you go up and right. Al³⁺ is a very small posative ion and F^1- is a small negative ion.

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

© copyright 1996, S.E. Van Bramer
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Last Updated: Friday, May 10, 2002 3:29:58 PM