* Neutral Atom: A neutral atom has a balanced number of protons (positive charge) and electrons (negative charge). The electrons are attracted to the nucleus, and this attraction holds the electron cloud close to the nucleus.
* Anion Formation: An anion forms when an atom gains one or more electrons. This extra electron(s) increases the overall negative charge of the ion. Now, there are more electrons repelling each other, but the attractive force from the nucleus remains the same.
* Increased Repulsion: The increased electron-electron repulsion causes the electron cloud to expand. This expansion leads to a larger ionic radius compared to the neutral atom.
In simpler terms: Imagine a balloon. The nucleus is like the air inside, holding the balloon (electron cloud) together. When you add more air (electrons), the balloon (electron cloud) expands.
Example: A chlorine atom (Cl) has 17 protons and 17 electrons. When it gains an electron to become a chloride ion (Cl-), it now has 17 protons and 18 electrons. The extra electron increases the electron-electron repulsion, causing the electron cloud to expand and the chloride ion to be larger than the chlorine atom.
