Chemistry
Chemistry
Spin
Electron spin acts like a bar magnet. Electrons with parallel spin have a magnetic repulsion that adds to the electrostatic repulsion. Electrons with anti-parallel spin have a magnetic attraction that reduces the electrostatic repulsion.
Orbitals
These rules apply to the s and p shells.
-
For a given set of orbitals, each of the orbitals will be singly occupied with an electron before becoming doubly occupied.
-
When there are unpaired electrons, it is more favorable for them to have the same spin rather than opposite spins.
Orbitals can hold either a single electron or two electons with opposite spin.
The s shells have a single slot.
The p shells have 3 orbitals. The first three electrons each occupy a separate orbital and all have parallel spins. The next 3 electrons pair up with opposite spin.
The d shells have 5 orbitals. The 3d and 4s shells fill up in some order.
The order in which orbitals are populated.
-
1s
-
2s 2p
-
3s 3p
-
4s 3d 4p
-
5s 4d 5p
-
6s 4f 5d 6p
-
7s 5f 6d 7p
Some atoms break the rules as it is a lower energy state to move an electron. The Noble metals 'borrow' an electron from the outer s shell to fill up the d shell.
Ions
Hydrogen can have \(H^-\) and \(H^+\) ions by adding or subtracting an election from the 1s orbital.
Helium can’t have a \(He^+\) ion becuse the nucleus can’t hold an electron in the 2s orbital.
Lithium is like Hydrogen and can have both positive and negative ions.
Berylium can’t have a \(Be^+\) ion becuse the nucleus can’t hold an electron in the 2p orbital.