📚 Topic Summary
Ionization energy is the energy required to remove an electron from a gaseous atom or ion. Successive ionization energies (first, second, third, etc.) always increase because it becomes progressively harder to remove an electron from an increasingly positive ion. Understanding the trends in ionization energy helps predict an element's chemical behavior and reactivity. In this worksheet, we'll work through some common problems to solidify your understanding of this key concept.
Ionization energy generally increases across a period (left to right) on the periodic table and decreases down a group (top to bottom). These trends are due to changes in effective nuclear charge and distance of the valence electrons from the nucleus.
🧪 Part A: Vocabulary
Match the term with its correct definition:
| Term |
Definition |
| 1. Ionization Energy |
a. The energy change when an electron is added to a gaseous atom. |
| 2. First Ionization Energy |
b. The minimum energy required to remove an electron from a neutral gaseous atom. |
| 3. Second Ionization Energy |
c. The energy required to remove an electron from a +1 ion in the gaseous phase. |
| 4. Electron Affinity |
d. The positive charge felt by an electron in an atom. |
| 5. Effective Nuclear Charge |
e. The energy required to remove the second electron from a neutral atom. |
Answers: 1-b, 2-e, 3-c, 4-a, 5-d
⚛️ Part B: Fill in the Blanks
Complete the following paragraph using the words provided: increases, decreases, noble gases, valence, left, right.
Generally, ionization energy _______ across a period from _______ to _______. This is because the effective nuclear charge experienced by the _______ electrons _______. Elements with very high ionization energies are the _______.
Answers: increases, left, right, valence, increases, noble gases
💡 Part C: Critical Thinking
Explain why the second ionization energy of an element is always greater than its first ionization energy.
Answer: The second ionization energy is always greater than the first ionization energy because after the first electron is removed, the atom becomes a positive ion. Removing an electron from a positive ion requires more energy due to the increased attraction between the remaining electrons and the nucleus.