2 Creating Energy-Level Diagrams The electrons occupy specific energy levels in the atom. The energy-level diagram is a method of representing an atom’s distribution of electrons throughout the various energy shells (n) and subshells or orbitals (l ).The energy-level diagrams can be extended to include all four quantum numbers.Experimental information about atomic matter shows that there are relationships between orbitals and their energy levels. Conventions have been established to attend to these observations.
3 Conventions for Creating Energy-Level Diagrams Pauli exclusion principle –no two electrons in an atom may have the same four quantum numbersno two electrons in the same orbital may have the same spinonly two electrons with opposite spins may occupy an orbitalaufbau principle – (German for “building up’)each electron is added to the lowest available energy orbitalHund’s rule –one electron is placed in each orbital at the same energy level before the second electron is placed
4 Conventions for Creating Energy-Level Diagrams Circles or squares are used to represent the orbitalsArrows are used to represent the electronsup represents one electron rotation (clockwise) while down the other (counter clockwise)there is no convention as to which one you must start with
5 Conventions for Creating Energy-Level Diagrams 2p3s3pO (z = 8)1s2s2p3s3pP (z = 15)1s2s2p3s3pAr (z = 18)
6 Conventions for Creating Energy-Level Diagrams Energy-level diagrams may be written in a vertical manner to exemplify the energy level subtleties.
7 Order of filling orbitals 2p3p4p6p5d4f5p4d3d2e-6e-10e-14e-8e-18e-32e-Order of filling orbitalsAs the number of energy levels and orbitals increase, so too does the complexity of the energy-level diagram.The diagram indicates nicely the order in which the orbitals are filled
8 Energy-Level Diagrams for ions The energy-level diagram is created in the same manner as the regular atom. However, a surplus or deficit of electrons are included.For anions – add the proper number of electrons using regular conventionsFor cations – remove the correct number of ions in the proper manner1s2s2p3s3pS 2- (z = 16)1s2s2p3s3pAl 3+ (z = 13)