Chemistry Molecules Exam


Practice Exam (test 4)

Name: __________________________

***This practice is longer than your actual exam!

This exam is meant for 50 minutes, but you have 60 minutes due to the circumstances.

This exam is worth 100 points.

All problems are worth different amounts of points.

The points per problem are indicated at the beginning of each problem.

Write concise and clear answers!

You should have ??? front and back pages. Scratch paper can be the blank pages on the backs of each page. Try to keep your answers within the space given. If you have to complete an answer in another location on the exam, please clearly indicate that.

You may use the laminated periodic table and constants sheets provided.

This is a closed note and book exam.

You only should have a calculator, a writing utensil, and your laminated sheet.

You must show work to receive full credit. You will earn partial credit for your work. If you don’t know how to solve the problems, try to show me how you would start. Also, if you can’t get the first part of a problem, don’t give up, but rather “make up” a numerical answer if needed for the next part.

Pay attention to units and sig figs.

It is a violation of academic integrity to speak to anyone about the content of the exam until it is returned to you.

  1. Rank the following bonds in order of increasing polarity: C-Br, C-Cl, C-F, and C-H.
  2. Draw the Lewis structure(s) of the following molecules. Include resonance structures if they exist.
    1. CO32-
    2. IF5
    3. CH3Br
  3. 6 points: Let us consider Zn:
    1. What is the electron configuration of Zn?
    2. What is the electron configuration of Zn2+?
  4. For the molecules whose Lewis structures are given below,
    1. Label the molecule as polar or non-polar, and show the direction of the net (molecular) dipole moment if one exists.
    2. Indicate the electron domain geometry and the molecular geometry of the central atom.
  5. Image result for ch2cl2

ii. Image result for clf3

  1. a. Draw the Lewis structure(s) of SO2.

b. What is the bond order of the SO bond based off your Lewis structure.

  1. A molecule AB3, where A and B represent two different atoms, has polar bonds and is nonpolar. What molecular geometry must this molecule be? What atom could atom A be?
  2. Draw the complete Lewis structure including resonance if applicable for OCN. Show the formal charge on each atom.
  3. Rank the following in terms of atomic radii from smallest to largest and provide a brief explanation:
    1. Li, K, and Na

________ < ________ < ________

(smallest) (largest)


    1. Ca2+, Ar, and Cl

________ < ________ < ________

(smallest) (largest)


  1. Let us think about first and second ionization energies.
    1. Does potassium (K) or calcium (Ca) have a higher first ionization energy (no explanation needed)?
  2. Describe why the second ionization energy of potassium (K) is much greater than the second ionization energy of calcium (Ca). Hint: think about electron configurations.
  3. Let us consider the element oxygen, O:
    1. How many valence electrons does O have? ________________
    2. How many core electrons does O have? _______________
    3. Below are various orbital diagrams of O. Circle the orbital diagram(s) below that are valid electron arrangements in the lowest energy state. In the space below, provide a brief explanation as to why certain orbital diagram(s) may be invalid.
      1. _______ _______ _______ _______ _______

1s 2s 2p

      1. _______ _______ _______ _______ _______

1s 2s 2p

      1. _______ _______ _______ _______ _______

1s 2s 2p

Explain why certain orbital(s) above are invalid:

  1. 6 points: Circle the radiation that corresponds to a higher energy in each pair (i.e. – circle one it­­­em in each row):

IR radiation

Gamma rays

Absorption of an electron in the hydrogen atom from n=1 to n=3

Absorption of an electron in the hydrogen atom from n=2 to n=4

Red light emitted

Blue light emitted

  1. Answer the following questions:
      1. Sketch a p orbital. How do the three p orbitals in a subshell differ from one another?
      2. Can the electron occupying the orbital be outside of the region of space you have just sketched? Explain.
  2. Given the atoms Br, O, Rb, and S:
    1. Which has the highest ionization energy?
    2. Which has the largest atomic radius?
  3. What is the condensed electron configuration for phosphorus (P) in the ground state? How many valence electrons does P have?
  4. Give the four quantum numbers of the valence electrons present in Zr2+. ***There is more than one correct answer!
  5. Perform the following conversions:
    1. 2.50 x 10-22 J into Hz
    2. 276 nm into J
    3. 400.0 MHz into J
    4. 225 GHz into nm
  6. The quantum numbers of Planet X are exactly like ours, except ml takes on the values of -2l to +2l in steps of 1 Sketch the periodic table is it would appear on Planet X through element 52. How many electrons are in each subshell (s, p, d, and f)? What is the atomic number of the first element with an electron in a d orbital? THIS IS A VERY HARD PROBLEM AND NOTHING THIS HARD WILL BE ON THE TEST!
  7. For the H-atom, calculate the following:
    1. ΔE in J for the n=1 to n=2 transition.
    2. Λ in nm for the n=2 to n=3 transition.
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