Principal shell shows the main energy level, in that there are some more energy levels. This is how the atomic structure is defined according to the Quantum Mechanical model of atom. So exactly why do subshells exist and all i don't know
b
Explanation:
February 7, 1863, was the day John Newlands published a paper outlining what would be known as “The Law of Octaves”. Newlands discovered if he ordered the known elements by increasing atomic weight, the chemical properties of the elements would be similar for every eighth group
