What is electron affinity?

Answer 1

Definition: (E_ea) of an atom or molecule is the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.

Now that we have this definition, how do we apply it in chemistry?

1. Identify patterns in the periodic table
2. Electron affinity increases upward for the groups
3. Electron affinity increases from left to right across periods of a periodic table
4. This happens because the electrons added to energy levels become closer to the nucleus
5. Electrons closer to the nucleus form a stronger attraction between the nucleus and its electrons

Answer 2

Electron affinity is the energy released when an electron is added to an atom. The trends are upward and towards the right of the periodic table.

Think about it like how badly an atom wants an electron. The halogens (the 7th column) want an electron SO BAD because they just want to be a noble gas, and it only takes 1 electron to be added. So they will have then HIGHEST electron affinity, and the most energy will be released.