Do Now: Complete Protons, Neutrons, and Electrons Practice Worksheet YWBAT • List the three rules for writing the electron configuration of elements Electron Configuration • Describes arrangement of electrons in an atom • Three rules 1. Aufbau Principle 2. Pauli Exclusion Principle 3. Hund’s rule Electron Configuration 1. Aufbau Principle a) An electron occupies the lowest energy orbital that can receive it. b) Fill electrons lowest to highest energy 2. Hund’s Rule - Orbitals of the same energy must be occupied by 1 electron before it can be occupied by two electrons 3. Pauli-Exclusion Principle - Each orbital can only hold 2 electrons with opposite spins The aufbau diagram shows the relative energy levels of the various atomic orbitals. Orbitals of greater energy are higher on the diagram. Practice Phosphorus has 15 electrons. Write the electron configuration for Phosphorus. Practice Phosphorus has 15 electrons. Write the electron configuration for Phosphorus. 1s22s22p63s23p3 Noble Gas Configuration 1. Find the element on the periodic table. 2. Go back to the last noble gas that was passed. 3. Write the symbol of the noble gas in brackets to start your electron configuration. 4. Continue your electron configuration using the row after the noble gas. Noble Gas Configuration Write the noble gas configuration for Osmium. - Osmium is element 76. - The last noble gas was Xenon. - Os: [Xe] 6s2 4f14 5d6 Quantum Number Review • Principle Quantum Number (n) – Energy level – Row on periodic table • Angular Quantum Number (l) – Sublevels (s,p,d,f) – # sublevels = principle quantum number • # of orbitals = n2 • Maximum number of electrons that can occupy an energy level is 2n2