Periodic Trends Worksheet



Periodic Trends Worksheet

Use the periodic table and your knowledge of periodic trends to answer the following questions.

1. Which atom in each pair has the larger atomic radius?

a) Li or K b) Ca or Ni c) Ga or B d) O or C e) Cl or Br

f) Be or Ba g) Si or S

2. What is the periodic trend for atomic size from top to bottom in a group? from left to right in a period?

Because each row adds an electron shell, elements get larger from top to bottom. Because elements’ nuclei get larger from left to right across a row, and pull harder on their valence electrons, elements get smaller from left to right across a period.

3. Why do atoms get smaller as you move left to right in a period? See 2.

4. Which element in each pair has the larger ionization energy?

a) Na or O b) Be or Ba c) Ar or Cl d) Cu or Ra e) I or Ne

f) K or V g) Ca or Fr h) W or Se

5. Explain the relationship between the relative size of an ion to its neutral atom and the

charge on the ions.

6. Which particle has the larger radius in each atom/ion pair?

a) Na, Na+ b) S, S2- c) I, I- d) Al, Al3+

7. What is ionization energy? What is first ionization energy?

Ionization energy is the energy needed to pull a valence electron off an atom. More than one electron can be removed this way, but the amount of energy needed increases with each electron. First ionization energy is the energy needed to pull the first electron off a neutral atom. When we talk only about “ionization energy,” we mean first ionization energy.

8. What is the periodic trend for first ionization energy?

As we move across a period from left to right, the valence electrons are held more and more tightly, so just as the atoms get smaller, more and more energy is needed to pull an electron off and the ionization energy increases. As we move down a group/family, the added electron shells make the atoms larger; attraction between electrons and protons falls off with distance, so the farther out the valence, the lower the ionization energy, which increases from top to bottom of a group.

9. Arrange the following groups of elements in order of increasing ionization energy.

a) Be, Mg, Sr Sr < Mg ................
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