Question

The trend for ionization energy is a general increase from left to right across a period. However, phosphorus (P) is found to have a higher first ionization energy value than sulfur (S). Explain this exception to the general trend in terms of electron arrangements and attraction/repulsion.

Answer 1

@FriedRice @Ciarán95

Answer 2

@Hero @ganeshie8 @HelpBlahBlahBlah

Answer 3

@asib1214

Answer 4

@Abmon98

Answer 5

@AccidentalAiChan @jgirl128 @Schleifspur @scapeplan @sunshao1 @SchoolKid

Answer 6

@Ciarán95 can u plz help me

Answer 7

Ye sure...what's wrong?

Answer 8

i just don't understand

Answer 9

I think this is to do with the electronic configurations of the two elements in their ground state. This is the way in which we assign the electrons (15 in phosphorus, 16 in sulfur) to the available orbitals at the different energy levels, starting with the lowest energy orbitals and working our way up. You need to know a bit about this in order to understand the question. Do you know what I'm talking about?

Answer 10

yes i do

Answer 11

Phosphorus has more stable half filled arrangement. So more energy is required to ionize it than sulfur.

Answer 12

okay

Answer 13

OK...brilliant! Here's just a recap of some of the rules we use when assigning these electrons to the given orbitals:

-Hund's Rule: If we have more than one orbital at any given energy level, then the electrons will occupy each orbital singly before occupying them in pairs.
-And, most importantly for this question, THERE IS A SPECIAL STABILITY ASSOCIATED WITH HAVING A FULL OR HALF-FULL SHELL OF ELECTRONS,

Let's look at sulfur first. This has 16 electrons, according to the periodic table. So let's start filling them into the orbitals (I'm going to assume you know what I'm doing here - 1s2 means 2 electrons in the 1s orbital, and so on...).

1s2 2s2 2p6 3s2 3p4.
Here's how the electrons (represented by the half-arrows) sit in the three 3p orbitals:


For phosphorus, the electronic configuration is:
1s2 2s2 2p6 3s2 3p3, and the 3p orbitals look like