Electron Configuration
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Electrons in Atoms Electron Configuration When we write electron configurations, we are writing the configurations of the electrons in the ground state. ground state - the lowest energy level of electrons. Summary # of Max orbitals electrons Starts at energy level s 1 2 1 p 3 6 2 d 5 10 3 f 7 14 4 A. General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins. A. General Rules Aufbau Principle Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule” A. General Rules Hund’s Rule Within a sublevel, place one e- per orbital before pairing them. “Empty Bus Seat Rule” WRONG RIGHT Electron Configuration List of subshells containing electrons Written in order of increasing energy Superscripts give the number of electrons Example: Electron configuration of neon number of electrons 1s2 shell 2s2 2p6 subshell By Energy Level First Energy Level only s orbital only 2 electrons 2 1s Second Energy Level s and p orbitals are available 2 in s, 6 in p 2 6 2s 2p 8 total electrons By Energy Level Third energy level s, p, and d orbitals 2 in s, 6 in p, and 10 in d 2 6 10 3s 3p 3d 18 total electrons Fourth energy level s,p,d, and f orbitals 2 in s, 6 in p, 10 in d, and 14 in f 2 6 10 14 4s 4p 4d 4f 32 total electrons By Energy Level The orbitals do not fill up in a neat order. The energy levels overlap Lowest energy level fill first. Order of Filling The 4s energy < 3d energy 4p 3d 4s 3p 3s 2p 2s 1s ___ ___ ___ ___ ___ ___ ___ ___ (finishes the n=3 shell) (starts the n=4 shell) Increasing energy 7s 6s 5s 7p 6p 5p 4p 4s 3p 3s 2p 2s 1s 6d 5d 4d 3d 5f 4f Electron Configuration Let’s determine the electron configuration for Phosphorus Need to account for 15 electrons Increasing energy 7s 6s 5s 7p 6p 6d 5d 5p 4d 4p 3s 2s 1s 4f 3d 4s 3p 5f The first two electrons go into the 1s orbital 2p Notice the opposite spins only 13 more to go... Increasing energy 7s 6s 5s 7p 6p 6d 5d 5p 4d 4p 5f 4f 3d 4s 3p 3s 2p 2s 1s The next electrons go into the 2s orbital only 11 more... Increasing energy 7s 6s 5s 7p 6p 5p 4p 4s 6d 5d 4d 5f 4f 3d 3p 3s 2p 2s 1s • The next electrons go into the 2p orbital • only 5 more... Increasing energy 7s 6s 5s 7p 6p 5p 4p 4s 6d 5d 4d 5f 4f 3d 3p 3s 2p 2s 1s • The next electrons go into the 3s orbital • only 3 more... Increasing energy 7s 6s 5s 4s 7p 6p 6d 5d 5p 4d 4p 3p • 3s 2s 1s 2p • • • 5f 4f 3d The last three electrons go into the 3p orbitals. One electron to each separate 3p orbitals 3 unpaired electrons = 1s22s22p63s23p3 The easy way to remember 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 1s • 2 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 1s 2s • 4 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s • 12 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s 6 2 3p 4s • 20 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s 6 2 10 6 3p 4s 3d 4p 5s2 • 38 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s 6 2 10 6 3p 4s 3d 4p 5s2 4d10 5p6 6s2 • 56 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s 6 2 10 6 3p 4s 3d 4p 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 • 88 electrons Fill from the bottom up following the arrows 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s • 2 2 6 2 1s 2s 2p 3s 6 2 10 6 3p 4s 3d 4p 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6 • 108 electrons 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s Writing Electron Configurations H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 S 1s2 2p 2s2 2p2 2p6 3s2 3p4 3p Learning Check Identify the element with the configuration written below Na A. 1s22s22p63s1 B. 1s22s22p63s23p6 Ar C. 1s22s22p63s23p64s1 K D. 1s22p83s1 E. 1s22s22p63s23p7 Inconceivable!!! Inconceivable!!! Identify the element with the configuration written below A. 1s2 2s2 2p6 3s2 3p5 Cl B. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 Sr C. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5 I Final notations A. Write the final two notations for Co. 4s2 3d7 B. Write the final three notations for Sn. 5s2 4d10 5p2 B. Notation Orbital Diagram O 8e- 1s 2s Electron Configuration 2 2 4 1s 2s 2p 2p B. Notation Longhand Configuration S 16e- 1s2 2s2 2p6 3s2 3p4 Core Electrons Valence Electrons Inner Electrons Shorthand Configuration S 16e 2 4 [Ne] 3s 3p C. Periodic Patterns s p 1 2 3 4 5 6 7 f (n-2) d (n-1) 6 7 © 1998 by Harcourt Brace & Company C. Periodic Patterns Period # energy level (subtract for d & f) Group # and # of valence of eGroups 1-2: group # = total # of valence eGroups 13-17: group # - 10 = total # of valence eColumn within sublevel block # of e- in sublevel C. Periodic Patterns Example - Hydrogen 1 2 3 4 5 6 7 1 1s 1st Period 1st column of s-block s-block C. Periodic Patterns Shorthand Configuration Core e-: Go up one row and over to the Noble Gas. Valence e-: On the next row, fill in the # of e- in each sublevel. 1 2 3 4 5 6 7 C. Periodic Patterns Example - Germanium 1 2 3 4 5 6 7 [Ar] 2 4s 10 3d 2 4p D. Stability Full energy level Full sublevel (s, p, d, f) Half-full sublevel 1 2 3 4 5 6 7 Orbitals fill in order Lowest energy to higher energy. Adding electrons can change the energy of the orbital. Half filled orbitals have a lower energy. Makes them more stable. Changes the filling order D. Stability Electron Configuration Exceptions Copper EXPECT: [Ar] 4s2 3d9 ACTUALLY: [Ar] 4s1 3d10 Copper gains stability with a full d-sublevel. D. Stability Electron Configuration Exceptions Chromium EXPECT: [Ar] 4s2 3d4 ACTUALLY: [Ar] 4s1 3d5 Chromium gains stability with a half-full d-sublevel; slightly lower in energy D. Stability Ion Formation Atoms gain or lose electrons to become more stable. Isoelectronic with the Noble Gases. 1 2 3 4 5 6 7 D. Stability Ion Electron Configuration Write the e- config for the closest Noble Gas EX: Oxygen ion O2- Ne 2O 10e [He] 2 2s 6 2p Electron Configuration Lists the shells containing electrons Written in order of increasing energy Element He C F Ne Al Cl Shell 1 2 2 2 2 2 2 2 3 4 7 8 8 8 3 7 Learning Check A. The electron configuration for sulfur 1) 2,6 2) 8,2,6 3) 2, 8, 6 B. The element in period 3 with two electrons in the outermost energy level 1) Mg 2) Ca 3) Be Learning Check Indicate the number of electrons in the final notation of the electron configuration for each: A. O 1) 4 2) 6 3) 8 B. Al 1) 13 2) 3 3) 1 C. Cl 1) 2 2) 5 3) 7 Learning Check For phosphorus, indicate if each configuration is (1) correct or (2) incorrect. Explain why or why not? A. 2, 2, 8, 5 1 or 2 B. 2, 8, 3 1 or 2 C. 2, 8, 5 1 or 2 D. 2, 6, 7 1 or 2 Solution For phosphorus, indicate if each configuration is (1) correct or (2) incorrect. Explain why or why not? A. 2, 2, 8, 5 2 Shell 2 holds 8e- B. 2, 8, 3 2 P has 15 electrons C. 2, 8, 5 1 Correct arrangement D. 2, 6, 7 2 Shell 2 holds 8e- Periodic Law All the elements in a group have the same electron configuration in their outermost shells Example: Group 2 Be 2, 2 Mg 2, 8, 2 Ca 2, 2, 8, 2 Learning Check Specify if each pair has chemical properties that are similar (1) or not similar (2): 1 A. Cl and Br B. 2 - 5 and 2 - 8 - 7 C. 2 - 4 and 2 - 8 - 4 1 D. P and S 2 E. O and S 1 2
![The electronic configuration of phosphorus is [Ne] 3s2 3p3](http://s3.studylib.net/store/data/008974852_1-8381577ce936fbfa611892c1a5f109cd-300x300.png)
