Electron Configurations Of Atoms & Ions Men & their Rules • Aufbau Principle: Start at the beginning (Electrons enter lowest energy level 1st) • Pauli Exclusion Principle: Only 2 allowed (Only 2 electrons allowed in any orbital) • Hund’s Rule: Stay solo as long as possible (For orbitals of equal energy, 1 electron enters each until all orbitals contain one before any pairs up.) Consequences of Aufbau Principle • Electrons enter orbitals in order of increasing energy levels. • This order is shown in text on page 111. • 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p But there are two exceptions, namely Cu & Cr, who subtract 1 from 4s and add it to 3d. Consequences of Pauli exclusion • The s orbital is filled with 2 electrons. • The 3 different orientations of the p orbital, px, py, & pz, each contain a max of 2 electrons • The 5 different orientations of d orbitals, dxy dxz, dyz, dx2-y2, & dz2, can have max of 2 each. • The 7 different orientations of f orbitals also only have 2 electrons for each suborbital. Consequences of Hund’s Rule • One electron is added to px, then 1 to py, then 1 to pz, before the second one is added to px. The 5th electron is then added to py, & 6th to pz. • The same pattern is observed for the d & f suborbitals. • NOTE: The single electrons all have parallel spins. When the 2nd electron is added to each suborbital, it spins in the opposite direction. Relating this to the periodic table: • The “s block” = Groups IA & IIA • The “p block” = Groups IIIB – VIII (13-18) • The “d block” = Transition elements (Groups IIIA-IIB; Groups 3-12) • The “f block” = Rare earth metals What this means… • You merely need to follow the periodic table to figure out electron configurations. • The block (s, p, d, & f) indicates where the last electrons go. • Follow the period numbers, 1-7, because these are your energy levels & then remember suborbitals penetrate differently. How can we apply this? • In our upcoming lab we will observe metals forming ions due to their electron configurations. • Different metals (s vs. d vs. p) will behave differently. • Transition metal ions usually have color. Setting up the lab • Mark 3 grids as shown on whiteboard, 3” x 4”. • We do not have NiSO4; place AgNO3 there instead. • We will use 4 glass slides, 3 vertical & 1 horizontal. • After you’ve observed color of solutions, add a drop of NaOH to each & note changes. • Repeat with addition of Na2CO3. • Write chemical formulas for rxns. Solutions for this lab: • • • • • 1.0 M NaCl & Na2CO3 0.5 M CaCl2 & NaOH 0.2 M MgSO4, AlCl3, CuSO4, & ZnCl2 0.1 M FeCl3 0.05 M AgNO3 Lab Report • You must answer all questions in handout. • You must relate electron configurations to what you observe & discuss this in the Conclusions section. • You can use the Internet to obtain extra information concerning these reactions.