Here's a breakdown:
* Neutral gaseous atom: We start with an atom in its gaseous state, not bonded to any other atoms.
* Electron addition: An electron is added to the atom's electron cloud.
* Negative ion: The addition of the electron results in the formation of a negatively charged ion.
* Energy change: This process can either release energy (exothermic, negative electron affinity) or require energy input (endothermic, positive electron affinity).
In simpler terms: Electron affinity measures how much an atom "wants" to gain an electron.
Here's an example:
Chlorine (Cl) has a high electron affinity. When a chlorine atom gains an electron to form a chloride ion (Cl-), energy is released. This means that chlorine has a strong attraction for electrons.
Key points to remember:
* Electron affinity is a thermochemical property, meaning it deals with energy changes.
* Electron affinity is usually expressed in electron volts (eV) or kilojoules per mole (kJ/mol).
* It's important to note that electron affinity is a periodic trend, generally increasing across a period and decreasing down a group.
