CHEE4S- Periodic Trends Definitions

What is shielding?

Electrons in the outer shells spend more time away from the nucleus. Shielding is the repulsion force from inner electrons against the valence electrons which reduces the electrostatic attractions between the outer electrons and the nucleus.

What is Effective Nuclear Charge? (Z_eff)

Effective Nuclear Charge is the charge experienced by a valence electron.
Z_eff = Z - σ
Z_{eff - charge experienced by outer e-}

_{Z - actual nuclear charge(atomic number)}

σ - # of inner electrons

More shielding, less Zeff

How do anion radii compare to the original atom?

They gain an e-, so the ionic radius increases

How do cation radii compare to the original atom?

They lose e-, so the ionic radius decreases

What is First Ionization Energy?

First Ionization Energy is the amount of energy needed to remove an outermost electron from a gaseous atom.

Energy is always added

What are the Exceptions to First Ionization Energy?

It requires more energy to pull an electron from a full d-subshell than a single electron in a p-subshell

(in the same period)

It requires more energy to pull an electron from a full s-subshell than a single electron in a p-subshell

(in the same period)

The single e- is easier to remove since it’s the only e- in the higher nrg subshell and is being shielded

How does the 2nd IE compare to the 1st IE?

The second IE is always greater than the first IE because the radius reduces after the first e- is removed (cations get smaller) so the nucleus achieves a stronger pull on the outermost e- because of coulombic attraction

Why does each element have a big increase in IE energy?

Because at a certain point, the IE will be really high because the electron config will drop a principal energy level, which makes the radius shrink much more (the nucleus will have a stronger pull on outer e-)

What is Electron Affinity?

The energy change that occu