principal quantum number

The principal quantum number, often labeled as "n," is a key concept in quantum physics that indicates the main energy level or shell where an electron resides within an atom. Think of it as a number that defines how far away the electron is from the nucleus—the larger the number, the farther the electron is generally located from the nucleus, meaning it has higher energy. It helps determine the size of the orbital and the energy of the electron, with lower numbers corresponding to closer, lower-energy levels, and higher numbers to farther, higher-energy levels.