ORBITALS S orbital spherical shape P orbital dumbbell shape D orbital 4 leaf clover shape F orbital asterik symbol 3 intersecting lines QUANTUM MECHANICS When an electron falls from a higher energy outer shell orbital to a lower energy inner shell orbital it emits electromagnetic energy whose frequency corresponds to the energy difference between the orbitals The different spectral series correspond to electronic transitions from outer shell orbitals to different inner shell orbitals m shell the transition is to inner shell n shell the transition is from outer shell ELECTRON SPIN AND THE PAULI EXCLUSION PRINCIPLE Electrons have spin which gives rise to a tiny magnetic field and to a spin quantum number m s Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers Effective Nuclear Charge Zeff The nuclear charge actually felt by an electron Electron shielding leads to energy difference between ns np and nf orbitals video about effective nuclear charge Zeff Z S Bottom line electrons are farther from the nucleus IMPORTANT PRINCIPLES Electron Configuration A description of which orbitals are occupied by electrons Degenerate Orbitals Orbitals that have the same energy level For example the three p orbitals in a given shell Ground State Electron Configuration The lowest energy configuration Aufbau Principle building up A guide for determining the filling order of orbitals Lower energy orbitals fill before higher energy orbitals An orbital can only hold two electrons which must have opposite spins Pauli Exc Principle If two or more degenerate orbitals are available follow Hund s rule Hund s Rule If two or more orbitals with the same energy are available one electron goes into each until all are half full The electrons in the half filled orbitals all have the same value of their spin quantum number ELECTRON CONFIGURATION The S block has a maximum of 2 electrons The D block has a maximum of 10 electrons The P black has a maximum of 6 electrons Exceptions in Expected vs Actual configuration Cr Expected Ar 4s 2 3d 4 Actual Ar 4s 1 3d 5 LiCl makes a red flame NaCl makes a yellow flame yellow flame sodium KCl makes a lilac flame Photon beam of light that behaves as a stream of small particles How many orbitals are in 4th shell A 16
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