Onlt two electon with opposing spings are allowed each orbitl is known as
1- pauli exclistion principle
2- Hund’s rule
3- aufbau principle
4 heisenberg uncertainty principle
Ho many valence electrons do the alkali earth metas possess
an excited electron in hydrogen atom emits a photon with a wavelength of 1093.9nm as it makes a transition to the n=3 energy level. from which level did the electron transition from?