Orbitals fill in order of increasing energy.
The order of filling is:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
The 4s orbital is filled before the 3d orbital as the 3d orbital has a higher energy than the 4s orbital.
The opposite spin helps to counteract the repulsion between electrons in the same orbital. Orbitals with the same energy are occupied singly and then paired when there is no unoccupied orbital left.
The electron configuration of krypton of atom number 36 is:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
The electron configuration of potassium K of atomic number 19 is
[Ar] 4s1
where [Ar] is the electron configuration of argon. first 30 elements:
The order of filling is:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
The 4s orbital is filled before the 3d orbital as the 3d orbital has a higher energy than the 4s orbital.
Each orbital can hold up to 2 electrons as long as they have opposite spins.
The opposite spin helps to counteract the repulsion between electrons in the same orbital. Orbitals with the same energy are occupied singly and then paired when there is no unoccupied orbital left.
| 1s 2s 2px 2py 2pz | |||||
| oxygen | ↿⇂ | ↿⇂ | ↿⇂ | ↿ | ↿ |
The electron configuration of krypton of atom number 36 is:
The electron configuration of potassium K of atomic number 19 is
where [Ar] is the electron configuration of argon. first 30 elements:
| element | atomic number | electron configuration |
| hydrogen | 1 | 1s1 |
| helium | 2 | 1s2 |
| lithium | 3 | 1s2 2s1 |
| beryllium | 4 | 1s2 2s2 |
| boron | 5 | 1s2 2s2 2p1 |
| carbon | 6 | 1s2 2s2 2p2 |
| nitrogen | 7 | 1s2 2s2 2p3 |
| oxygen | 8 | 1s2 2s2 2p4 |
| fluorine | 9 | 1s2 2s2 2p5 |
| neon | 10 | 1s2 2s2 2p6 |
| sodium | 11 | 1s2 2s2 2p6 3s1 |
| magnesium | 12 | 1s2 2s2 2p6 3s2 |
| aluminium | 13 | 1s2 2s2 2p6 3s2 3p1 |
| silicon | 14 | 1s2 2s2 2p6 3s2 3p2 |
| phosphorus | 15 | 1s2 2s2 2p6 3s2 3p3 |
| sulfur | 16 | 1s2 2s2 2p6 3s2 3p4 |
| chlorine | 17 | 1s2 2s2 2p6 3s2 3p5 |
| argon | 18 | 1s2 2s2 2p6 3s2 3p6 |
| potassium | 19 | 1s2 2s2 2p6 3s2 3p6 4s1 |
| calcium | 20 | 1s2 2s2 2p6 3s2 3p6 4s2 |
| scandium | 21 | 1s2 2s2 2p6 3s2 3p6 4s2 3d1 |
| titanium | 22 | 1s2 2s2 2p6 3s2 3p6 4s2 3d2 |
| vanadium | 23 | 1s2 2s2 2p6 3s2 3p6 4s2 3d3 |
| chromium | 24 | 1s2 2s2 2p6 3s2 3p6 4s1 3d5 |
| manganese | 25 | 1s2 2s2 2p6 3s2 3p6 4s2 3d5 |
| iron | 26 | 1s2 2s2 2p6 3s2 3p6 4s2 3d6 |
| cobalt | 27 | 1s2 2s2 2p6 3s2 3p6 4s2 3d7 |
| nickel | 28 | 1s2 2s2 2p6 3s2 3p6 4s2 3d8 |
| copper | 29 | 1s2 2s2 2p6 3s2 3p6 4s1 3d10 |
| zinc | 30 | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 |