Question

Why does fluorine have a higher ionization energy than iodine?

Answer 1

look at the periodic table, what do you know about electrons (and consequently the radius of an element) as you go down a period?

Answer 2

period = column

Answer 3

I don't get it?

Answer 4

okay, how many electrons does fluorine have and how many does iodine have?

Answer 5

F has 7?

Answer 6

well valence electrons, yes, 7. but it has a total of 9 right?
iodine has 53!

so lets say if you had a bunch of elastic bands and you kept putting one over the other (forming a ball) which one would be bigger iodine or fluorine?

Answer 7

Iodine?

Answer 8

yeah, so if you keep adding electrons to an atom, it's radius is gonna get larger and larger. Due to this, there is repulsion between the electrons close to the outside and the ones closer to the nucleus (since they're both negatively charged). This repulsion makes it easier to remove these electrons since they're held less tight

Answer 9

in chemistry, they refer to the attraction electrons experience towards the nucleus Zeff "effective nuclear charge".

Answer 10

just adding to that -
both fluorine and iodine are in same group, so their "effective nuclear charge" is same.

but since the valence electrons in iodine are *farther* away from the nucleus compared to the valence electrons in fluorine, it is easy to remove electrons from iodine. thats the reason iodine has less ionization energy compared to fluorine.

this is true in every group : ionization energy decreases going down a group.

Answer 11

the effective nuclear charges of these are not the same though

Answer 12

although everything else you mentioned is on key

Answer 13

@aaronq define 'effective nuclear charge'

Answer 14

attraction experienced by an electron in a multi-electron atom

Zeff= Z -S

Z = protons

S = screening constant

you can estimate S with slater's rules

Answer 15

ok you refering to S.. fine :)

Answer 16

(: