Electron Affinity, Ionization energy, and Effective Nuclear Charge

[Stevin1H]

I'm having a hard time understanding why the trends are the way they are for Electron Affinity and Ionization energy. Can someone please explain this?

Also, what is effective nuclear charge and how is that represented in the periodic table?

[Chem_Mod]

Effective nuclear charge is essentially the amount of attraction an electron feels towards its nucleus. The higher the nuclear charge, the more attraction there is. This is based on the # of protons, # of shells, and degree of shielding.

Ionization energy is the amount of energy you need to add to remove an electron. Thus, if you have a higher effective nuclear charge, there is more attraction, which requires more energy to remove that electron. First ionization energies generally increase as you go up and across the periodic table because higher effective nuclear charge.

Electron affinity is the amount of energy released when you add an electron to an atom in its gaseous state. It generally increases as you go up and right. For example, Chlorine has a high electron affinity because it only needs one electron to complete an octet, and thus, it really wants that electron to be stabilized.

[Sarah Jeong 4F]

Electronic Affinity & Ionization energy are the same concept, where electronic affinity is how strong the element wants the e-, and the ionization energy is how strong energy is needed to remove a e-. Electronic Affinity and Ionization energy are stronger as you go up and to the right, because it takes more energy to remove e-from shells that are closer to the nucleus(ie. to the top) and bc it takes more energy to remove e- that are closer to a full octet(ie. to the right).
Effective nuclear charge is net positive charge that an outer shell e- experiences in an atom, and on the periodic table increases as you go up and to the right. Stronger up bc there are fewer inner e- to shield the nucleus. Stronger right bc the number of protons increase without an increase to the inner e-.