📚 Topic Summary
Ionic radius refers to the size of an ion. When an atom loses electrons to form a positive ion (cation), it becomes smaller because the remaining electrons are more strongly attracted to the nucleus. Conversely, when an atom gains electrons to form a negative ion (anion), it becomes larger because the increased electron-electron repulsion expands the electron cloud. This size difference profoundly influences how ions interact with other ions and molecules.
The impact on chemical reactivity is significant. Smaller, highly charged ions tend to form stronger bonds due to their higher charge density. This affects lattice energy, solubility, and the overall stability of compounds. Larger ions, on the other hand, might lead to weaker bonds but can enhance reactivity in specific reactions due to steric effects and polarizability.
🧪 Part A: Vocabulary
- 🔎 Match the term with its definition:
| Term |
Definition |
| Ionic Radius |
a) The energy required to remove an electron from a gaseous atom or ion. |
| Cation |
b) A negatively charged ion formed by gaining electrons. |
| Anion |
c) The distance from the nucleus to the outermost electron in an ion. |
| Ionization Energy |
d) A positively charged ion formed by losing electrons. |
| Charge Density |
e) The amount of electric charge per unit volume. |
(Answers: Ionic Radius - c; Cation - d; Anion - b; Ionization Energy - a; Charge Density - e)
⚗️ Part B: Fill in the Blanks
As an atom ________ (1) an electron, it forms a(n) ________ (2) which has a ________ (3) ionic radius compared to its neutral atom. Conversely, when an atom loses an electron, it becomes a(n) ________ (4) with a ________ (5) ionic radius.
(Answers: 1- gains, 2- anion, 3- larger, 4- cation, 5- smaller)
🤔 Part C: Critical Thinking
Explain how the difference in ionic radii between $Na^+$ and $Cl^-$ ions contributes to the formation of the stable $NaCl$ crystal lattice. Consider the electrostatic interactions and packing efficiency.