Question

Which have the higher first ionization energy? Explain answer choice.

1) Fe or Ru

2) P or S

3) Br or K

4) Cd or In

Answer 1

Fe and Ru

electronic configuration of Fe is [Ar] 3d6 4s2

electronic configuration of Ru is [Kr] 4d6 5s2

both are almost same outer electronic configuration so we should look at the size Ru is bigger size electroms far away from the nucleas where as Fe electrons are near to nucleas

so Fe is answer

2)

P electronic configuration

[Ne] 3s2 3p3

S is

[Ne] 3s2 3p4

P is half filled so answer is P

3)

answer is Br

because electro positive elements K will have less Ionization energy

4)

Answer is Cd

Cd electronic configuration is [Kr] 4d10 5s2

full filled configuration difficult