, Describes the behavior of electrons in terms of quantized energy changes (a quantum is a unit of energy) The behaviour of electrons is described in terms of the probability of finding an electron in a given region of space. ORBITAL: The region of space around a nucleus in which an electron is most likely to be found. GROUND STATE: The Lowest energy level of an atom. QUANTUM NUMBERS: Used to describe an electron in an orbital. (like an address) In 1926, Schrödinger formulated mathematical equations of the energy waves of electrons, which led to the formation of models representing the shape and orientations of the most probable distributions of electrons about the nucleus. 1) n – The principal quantum number. Describes the size of an orbital. n = 1, 2, 3, to infinity The number of the energy level relates to the average distance of the orbital from the nucleus of an atom. 2 Each energy level has a certain number (n ) of orbitals in it. Energy Level n in that energy level = 1 2 3 4 etc. Number of Orbitals 1 4 9 16 n2 …continued 2) ℓ – The second quantum number. Also called the “subsidiary” or “azimuthal” quantum number. Designates the shape of of an orbital. In each level, n, the number of orbital shapes, ℓ, is equal to: 0<ℓ