Which one of the following is the correct electronic configuration of chlorine?

Chlorine is a chemical element with the atomic number 17, meaning a neutral chlorine atom contains 17 electrons. These electrons are distributed across energy levels or shells according to the Bohr model. The first shell (K) can hold a maximum of 2 electrons, and the second shell (L) can hold a maximum of 8 electrons. For chlorine, after filling the first two shells with 10 electrons (2 + 8), the remaining 7 electrons occupy the third shell (M). This results in an electronic configuration of 2, 8, 7. The presence of 7 valence electrons in its outermost shell makes chlorine a highly reactive nonmetal, as it seeks to gain one electron to achieve a stable octet configuration similar to the noble gas argon.