The element with an atomic number of 20 is calcium (Ca).
The electron configuration for calcium (Ca) is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
This configuration represents the distribution of electrons in the various energy levels (shells) and sublevels (orbitals) of the calcium atom. The numbers represent the maximum number of electrons each energy level or sublevel can hold. In this case, the electrons are distributed as follows:
1s²: 2 electrons in the first energy level (1s sublevel)
2s² 2p⁶: 8 electrons in the second energy level (2s and 2p sublevels)
3s² 3p⁶: 8 electrons in the third energy level (3s and 3p sublevels)
4s²: 2 electrons in the fourth energy level (4s sublevel)
The total number of electrons in calcium is 20, matching its atomic number.