[hkalfighter]

i set some situations and explained them in terms of screening effect but i dont see the term ' screening effect ' when some books explain them .
for example ,
1) S has smaller first ionization enthalpy than O does
2) He has smaller first IE than Ar
3) Going down a group , the radii are increasing
etc
my books explain that there are more inner e- shells , the distance between nucleus and outermost e- increases , the attraction between them then decreases .
my explanation is that there are more inner e- shells , the outermost e- is more screened by the inner e- so the first IE decreases and radius increase.
i just wonder if i m right to explain like this , if it's wrong , when can i apply screening effect and when does screening effect outweight the positive nuclear charge
thx for any reply

Edit: Please don't abuse formatting

[Mitch]

1.) Oxygen has a larger first ionization energy than Sulfur.
2.)Helium has a larger first ionization energy than Argon.
3.)That seems fine.

[hkalfighter]

nono , i made something wrong
1) Oxygen has larger first IE than S
2) He has greater first IE than Ar
i want the explanation of these facts

[xiankai]

its not wrong to include shielding effect (i prefer to call it this way instead of screening ), its just that there are other factors too.

if the books didnt use the term, it may be because its implied. a greater atomic radius also means the outer electron is shielded by the attractive charge of the nucleus more effectively.