## Special elements

Jedrick Zablan 3L
Posts: 68
Joined: Sat Aug 17, 2019 12:17 am

### Special elements

Hello! Professor Lavelle was talking about specific elements like chromium that don't follow typical electron configuration. Can anyone tell me what are the other ones pls. :)

Christine Honda 2I
Posts: 116
Joined: Sat Sep 14, 2019 12:17 am

### Re: Special elements

The two main exceptions are Chromium ([Ar]3d^5 4s^1) and Copper ([Ar] 3d^10 4s^1)

These are exceptions to the general rule because a completely full or half full d sub-level is more stable than a partially filled d sub-level.

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

### Re: Special elements

There are two exceptions:

Chromium:
Which should be [Ar] $3d^{4}$ $4d^{2}$ according to the systematic pattern normally used
However, it is actually [Ar] $3d^{5}$ $4d^{1}$

Copper
Which should be [Ar] $3d^{9}$ $4d^{2}$ according to the systematic pattern normally used
However, it is actually [Ar] $3d^{10}$ $4d^{1}$

The reasons for these exceptions are that the 3d orbital is lower energy when it is symmetric, either with 5 electrons or 10 electrons. So when the 3d orbital only has 4 or 9 electrons, one electron drops from the 4s orbital to make the 3d orbital symmetrical.