AP Chemistry - Periodic Trends Take-Home Quiz

Answers to the following questions should be typed, spell-checked and proof-read.

1. We expect the atomic radius to increase going down a group in the periodic table. Can you suggest why the atomic radius of hafnium breaks this rule? (See data below)

Atomic Radius

Sc 1.57

Ti 1.477

Y 1.693

Zr 1.593

La 1.915

Hf 1.476

 2. Three elements have the electron configurations 1s22s22p63s23p6, 1s22s22p63s2, and 1s22s22p63s23p64s1. The first ionization energies of the three elements (not necessarily in the same order) are 0.4189, 0.7377, and 1.5205 MJ/mol. The atomic radii are 1.60, 0.94, and 1.97 A. Identify the three elements and match the appropriate values of ionization energy and atomic radius to each configuration.

 3. The ionization energies for the removal of the first electron in Si, P, S, and Cl are as listed below. Briefly rationalize this trend and any unusual aspects of the trend.


1st Ionization Potential (kJ/mol)









 4. In general as you move across the periodic table from the left to the right the electron affinity of the elements increases (the value becomes more negative). However when going from the Carbon group to the nitrogen group there is a large decrease (the value gets more positive). Explain the general trend and the exception to that trend.

5. Predict the relative size of the carbon ions C+2, C+4, C-4, and explain your predictions.

6. Imagine that there was a property second electron affinity. This would be the amount of energy given off when an atom gains its second electron (in other words the -1 ion gains another electron to become -2). What would the general trend be across the second row of the table? What "bumps" would be found in the trend? Be sure to list the second row elements in order of increasing second EA and explain the trend and the bumps.

 7. Use your knowledge of the periodic trends to explain why sodium, magnesium and aluminum have the common charges that they do. In other words why is sodium +1 not +2 or +3? Why is Mg +2 not +1 or +3 etc?

8. Explain all 5 trends (IP, EN, EA, AR, and IR) as you go down the chart. (Tell me both what the trend is and WHY).