1
which member of each pair has the greater negative electron affinity?
a) se or br
b) si or al
c) na or cl
9. which member of each pair has the larger radius?
a) ca or mg
b) al or p
c) f-1 or f
10. which member of each pair has the higher ionization energy?
a) he or ne
b) na or mg
c) ca or ca +2

Here's what I find.

Explanation:

8. Electron affinity

The atom that is closer to having a complete valence shell (is further to the right in the Periodic Table) will have the greater electron density. The correct answers are:

(a) Br  

(b) Si

(c) Cl

9. Atomic radius

(a) Ca.  Ca is one period closer to the bottom of the Periodic Table. It has one more electron shell than Mg, so its valence electrons are further from the nucleus.

(b) Al. P is two atoms to the right of Al, so it has two more protons in the nucleus. Its valence electrons are held more tightly, so it is the smaller atom.

(c) F⁻. An anion is always larger than its neutral atom the added electron increases electron repulsions. The electrons move further out so they can reduce these repulsions.

10. Ionization energy

(a) He.  He is  a smaller atom, so its electrons are closer to the nucleus and more difficult to remove.

(b) Mg. Mg is to the right of Na and has a filled 3s subshell. Both factors make it more difficult to remove an electron.

(c) Ca²⁺. Once you have removed the two valence electrons from an atom of Ca, you have exposed its argon-like inner core. It takes more energy to remove an electron from a completed shell.