The electronic configuration you provided, 1s2, 2s2, 2p6, 3s2, 3p5, represents the distribution of electrons in the various energy levels and orbitals of an element.
To determine the atomic number of the element, we need to count the total number of electrons in the configuration. Each orbital can hold a specific number of electrons:
- The 1s orbital can hold a maximum of 2 electrons.
- The 2s orbital can hold a maximum of 2 electrons.
- The 2p orbital can hold a maximum of 6 electrons.
- The 3s orbital can hold a maximum of 2 electrons.
- The 3p orbital can hold a maximum of 6 electrons.
By summing up the electrons in each orbital, we find that the total number of electrons is:
2 (1s) + 2 (2s) + 6 (2p) + 2 (3s) + 5 (3p) = 17
Therefore, the atomic number of the element is 17.