Ch.3 #19 (6th Edition)

[005115864]

Hi! Can someone please explain to me why it is more favorable to take an electron from the p subshell if it is already half filled?

I thought half-filled subshells were most favorable so taking an electron from something that is already half-filled will make the atom less stable?

Problem: Sb3+
Answer: [Kr]4d105s2

[Chem_Mod]

The rule of thumb is to take electrons from the highest energy subshell. In this case, you would take away from 5p since that is the highest energy (you can visualize this using an orbital diagram). Taking electrons from highest energy subshell would give you a more stable atom than if you took an electron from a lower energy subshell.

[timschaeffer Dis 1J]

It helps me to think about it this way:

The electrons farthest away from the nucleus will be taken away from the atom first (because they are further away from the nucleus attractive positive charge and therefore less tightly held). The electrons in the highest energy shell are always the furthest away from the nucleus, so this means that an electron in the n=5 shell will be taken away before any electron in the n=4 shell (regardless of whether or not the 4p shell is half filled).