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The principal energy level, also known as the principal quantum number , is the region or shell outside the nucleus of the atom in which an electron can be found without losing or gaining energy, and with the lowest energy possible. The main energy levels have in turn energy sublevels. These sublevels are known as the secondary or azimuthal quantum number (l) .
Representation of energy levels
To contain all the electrons in an atom of any of the currently known elements only 7 energy levels are needed. These levels are represented by letters, which are K, L, M, N, O, P, Q , or by numbers ranging from 1 to 7, where 1 is the lowest energy level and 7 is the highest energy level. .
Each main energy level has a specific number of electrons and can contain up to 2n 2 electrons, where n is the number of the level. Thus, the first level can contain up to 2 electrons 2 x (1) 2 = 2; the second up to 8 electrons, 2 x (2) 2 = 8; the third up to 18, 2 x (3) 2 = 18, and so on. Therefore, the equation to calculate the number of electrons in each energy level is X= 2n 2
The energy associated with an energy level increases as the distance from the nucleus increases. For example, if an electron is in the seventh energy level, it has much more energy associated with it than an electron in the first energy level.
energy sublevels
Each main energy level contains an energy sublevel that is made up of a specific number of orbitals, and in each of them there can be no more than two electrons. Like the main energy levels, the energy sublevels are represented by letters, in this case they are s, p, d, f.
Each main energy level has a sublevel that contains an s (1s) orbital , therefore it can contain a maximum of two electrons . The electrons in this orbital are called s-electrons and have the lowest energy of all the electrons in that principal energy level. This shell can contain a maximum of 2 electrons .
Each major energy level above the first contains one s orbital and three p orbitals . A set of three p orbitals called a p subshell can hold a maximum of six electrons . Therefore, the second level can contain a maximum of eight electrons , that is, two in the s orbital (2s) and 6 in the three p orbitals (2p).
Each major energy level above the second contains, in addition to one s orbital and three p orbitals, a set of five d orbitals called a d subshell, which can hold a maximum of ten electrons . Thus, the third shell contains a maximum of 18 electrons : 2 in the s orbital, 6 in the three p orbitals, and 10 in the five d orbitals.
The fourth level and higher levels, in addition to all above, also have an f subshell that contains seven f orbitals, and which can hold a maximum of 14 electrons . Thus, the fourth shell can contain up to 32 electrons : 2 in the s orbital, 6 in the three p orbitals, 10 in the five d orbitals, and 14 in the seven f orbitals.
Below are the tables that summarize all the information explained above:
Table energy levels and sublevels
| Energy levels ( n ) | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| sublevels | yes | s p | s p d | s p d f |
| Number of orbitals of each type | 1 | 1 3 | 1 3 5 | 1 3 5 7 |
| Orbital naming | 1s | 2s 2p | 3s 3p 3d | 4s 4p 4d 4f |
| Maximum number of electrons in orbitals | 2 | 2 – 6 | 2 – 6 – 10 | 2 – 6 – 10 -14 |
| Maximum number of electrons per level | 2 | 8 | 18 | 32 |
Sources
Bautista, C. [Learning chemistry].(March 31, 2020). Energy levels [Video File]. Youtube. https://youtu.be/p3v5b81E6NQ
