Electron Configuration

Electron Configuration

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  Electron configuration D.M K.M S.HZ.M I.S
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  Contents Introduction: Learning Objectives Arrangementof electrons in an atom 2 Atomic orbitals Electron configuration Filling rules for electron orbitals Energy levels and sublevels Examples and questions
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  Introduction: Learning Objectives 1.Describe the structure of energy levels 2. Define s, p and d orbitals, and describe their shapes 3. Describe the rules for assigning electrons to subshells 4. Deduce the electron configuration of an atom from its atomic number 5. Compare electron configurationsof atom and ion
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  Electrons exist inlayers called shells (the shells can also be called energy or principal levels). The number of shells is depends on the number of electrons. Arrangement of electrons in an atom. Energy levels Every shell has certain maximum number of electrons that can contain and it is calculated by the following formula: 2n2, where n is the order of energy level 1st level holds a maximum of 2 electrons 2nd level holds a maximum of 8 electrons 3rd level holds a maximum of 18 electrons This electron arrangement is written as 2, 8, 18.
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  What is theelectron arrangement for 15P? 15P is a neutral atom with atomic number 15, subsequently it has 15 electrons. Arrangement of electrons in an atom. Energy levels 15 electrons are distributed to shells starting from nearest to nucleus. The 1st energy can hold maximum 2 electrons, the 2nd – 8 electrons. 5 electrons will be arranged in the 3rd shell & there are place for 13 more electrons. 3rd level holds 5 electrons out of 18 maximum 2nd level holds 8 electrons 1st level holds 2 electrons This electron arrangement for 15P is written as 2, 8, 5.
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  Levels themselves dividedinto sublevels & sublevels consist of certain number of orbitals. Sublevels are different from one another by number of orbitals and their shape. Arrangement of electrons in an atom. Energy sublevels & orbitals There are 4 types of sublevels: s, p, d and f. Sublevel s p d f Number of orbitals 1 3 5 7 Shape of orbitals sphere dumbbell
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  Each orbital canhold TWO electrons. Maximum Number of Electrons In Each Sublevel Maximum Number Sublevel Number of Orbitals of Electrons s 1 2 p 3 6 d 5 10 f 7 14 Arrangement of electrons in an atom. Energy sublevels & orbitals The shapes of orbitals show the places where electrons most probably can exist near nucleus. Orbitals within the a sublevel are located in different directions.
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  4f 4d 4p 4s n = 4 3d 3p 3s n= 3 2p 2s n = 2 1s n = 1 Energy s s s s p p p d d f Arrangement of electrons in an atom. Energy sublevels & orbitals The 1st energy level has only s sublevel The 2nd energy level has s and p sublevels The 3rd energy level has s, p and d sublevels The 4th energy level has s, p, d and f sublevels Sublevels also differ from one another by energy. Sometimes a sublevel of a lower shell might have higher energy than the sublevels of higher shell. For example, 3d sublevel of 3rd shell has higher energy than 4s sublevel of 4th shell.
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  • Hund’s Rule •Within a sublevel, place one electron per orbital before pairing them. • “Empty Bus Seat Rule” • Pauli Exclusion Principle • Each orbital can hold TWO electrons with opposite spins. WRONG RIGHT RIGHT WRONG Filling rules for electron orbitals • Aufbau Principle • Electrons fill the lowest energy orbitals first. • “Lazy Tenant Rule” 3d 5s 5p 6p 2s 3s 4s 5s 6s 7s 1s 2p 3p 4p 5p 6p 3d 4d 5d 6d 4f 5f 1s 2s 2p 3s 3p 4s 4p 4d 6s 7s 6d 4f 5f 5d Energy
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  Filling rules forelectron orbitals Energy levels nucleus Upside-down house 1 2 3 4 5 6 7 s p d orbitals sublevels (flats) shells electrons Remember the row of filling of orbitals! 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 …
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  1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 3d 4d 5d 6d 4f 5f 1s 2s 2p3s 3p 4s 3d 4p … 2 2 6 2 6 2 10 6 Electron configuration
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  How to deducean electron configuration? Remember the row of filling of orbitals! Example 1: Electronformula for 11Na: Short electron formula: ...3s1 3 – shell; s – sublevel; 1 – number of е– on the outer shell (= number of valence е–) Example 2: Electronformula for 16S2- First: e = Z – C = 16 – (–2) = 18 Then: 1s2, 2s2, 2p6, 3s2, 3p6 2 + 2 + 6 + 1 = 11 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 … We need to know the number of electrons! 1s2, 2s2, 2p6, 3s1 Z = 11 ; e = 11 (because the charge is 0) *EXCEPTIONS! 24Cr: 1s2 2s2 2p6 3s2 3p6 4s1 3d5 29Cu: 1s2 2s2 2p6 3s2 3p6 4s1 3d10
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  ➢ As -Arsenic ( Z=33, e=33): 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p3 Examples and questions ➢ Cu - Copper( Z=29, e=29) 1s2 2s2 2p6 3s2 3p6 4s1 3d10 ➢ Cr - Chromium( Z=24 , e=24) 1s2 2s2 2p6 3s2 3p6 4s1 3d5 1s2 2s2 2p6 3s2 3p6 3d6 not 1s2 2s2 2p6 3s2 3p6 4s2 3d4 ➢ S - Sulfur ( Z=16, e=16): 1s2 2s2 2p6 3s2 3p4 ➢ F - Fluorine ( Z=9, e=9): 1s2 2s2 2p5
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  Thank You!