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Orbital Diagrams and Electron Configuration

Orbital Diagrams and Electron Configuration. Drawing orbital diagrams gives information not only about the orbitals that are/have been filled but also about the number of unpaired electrons. Orbital diagrams can be cumbersome!!. Electron Configuration.

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Orbital Diagrams and Electron Configuration

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  1. Orbital Diagrams and Electron Configuration • Drawing orbital diagrams gives information not only about the orbitals that are/have been filled but also about the number of unpaired electrons. • Orbital diagrams can be cumbersome!!

  2. Electron Configuration • A short-hand notation is commonly used in place of orbital diagrams to describe the electron configuration of an atom. • Electron configuration: • a particular arrangement of electrons in the orbitals of an atom

  3. Another way of expressing electron distribution:Electron Configurations • Know relative energies of orbitals • Pauli exclusion principle • Distribution of electrons among the various orbitals = Electron configuration eg: Carbon: 1s2 2s22p2 6 electrons

  4. Electron Configurations • Each component consists of • A number denoting the energy level (n), • A letter denoting the type of orbital (l), • - A superscript denoting the number of electrons in those orbitals.

  5. Electron Configuration • The electron configuration tells the number of electrons found in each subshell using superscripts • If there are three electrons in a 2p subshell, we would write: 2p3 where the superscript (3) indicates the number of electrons in that subshell

  6. 1s 2s 2p 3s Electron Configuration • The orbital diagram for an O atom: The electron configuration for an O atom: 1s22s22p4

  7. 1s 2s 2p 3s 3p 4s Orbital Diagrams & Electron Configurations The orbital diagram for potassium. Z = 19 so there are 19 electrons And number of subshells (s,p,d..) and orbitals per energy level (n) Electron configuration of K: 1s2 2s22p6 3s23p6 4s1

  8. Electron Configuration To determine the electron configuration of an atom (or ion) without first writing the orbital diagram: • determine the number of electrons present • add electrons to each subshell in the correct filling order until all electrons have been added • use the “diagonal” diagram to help determine the filling order

  9. Electron Configuration Example: Write the electron configuration of a Mn atom (Z = 25). 1s2 2s22p6 3s23p6 4s2 3d5

  10. Electron Configuration can be written for ions as well Example: Write the electron configuration of an O2- ion (Z = 8). An O2- ion has 8 protons and 10 electrons 1s22s22p6

  11. Electron Configuration Write the electron configuration of a krypton atom (Z = 36). 1s22s22p63s23p64s23d104p6 This is the Kr “core”  [Kr] • The noble gas “core” can be used to write the electron configuration of an elementusing • core notation: • noble gas “core” + valence electrons

  12. Core notation To write the electron configuration using the core notation: • Find the Noble Gas that comes before the atom. • Determine how many additional electrons must be added beyond what that noble gas has. (= Atomic number of atom minus atomic number of noble gas) • Determine the period that element is in. (This determines the value of n of the s subshell to start with when adding extra electrons) • Add electrons starting in that “n” subshell

  13. Electron Configuration Write the core electron configuration of Sr (Z = 38). Previous noble gas: Kr (Z = 36) Extra electrons: 38 (e of Sr) - 36 = 2 Period number of Sr: 5 So: Kr core plus 2 extra e- starting in 5s [Kr] 5s2

  14. Electron Configuration Write the core electron configuration of Br (Z = 35). Previous noble gas: Ar (Z = 18) Extra electrons: 35 - 18 = 17 Period number: 4 So: Ar core plus 17 extra e- starting with 4s [Ar] 4s23d104p5

  15. Isoelectronic Series • When atoms ionize, they form ions with the same number of electrons as the nearest (in atomic number) noble gas. Na = 1s22s22p63s1 = [Ne]3s1 Na+ = 1s22s22p6 = [Ne] Cl = 1s22s22p63s23p5 = [Ne]3s23p5 Cl- = 1s22s22p63s23p6= [Ar]

  16. Isoelectronic Series • N (7 e-): 1s22s22p3 • O (8 e-): 1s22s22p4 • F (9 e-): 1s22s22p5 • N3- (10 e-): 1s22s22p6 = [Ne] • O2- (10 e-): 1s22s22p6 = [Ne] • F- (10 e-): 1s22s22p6 = [Ne]

  17. Isoelectronic Series • Na (11 e-): 1s22s22p63s1 • Mg (12 e-): 1s22s22p63s2 • Al (13 e-): 1s22s22p63s23p1 • Na+ (10 e-): 1s22s22p6 = [Ne] • Mg2+ (10 e-): 1s22s22p6 = [Ne] • Al3+ (10 e-): 1s22s22p6 = [Ne]

  18. 1A Ionsof the highlighted elements are isoelectronicwith Ne. 8A H 2A He 3A 4A 5A 6A 7A Li Be B C N O F Ne Na Mg Al Si P S Cl Ar 7B 8B 8B 8B 1B 2B 3B 4B 5B 6B K Ca Sc Ti V Cr Fe Co Ni Cu Zn Ga Ge As Se Br Kr Mn Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Md No Lr Fm

  19. Isoelectronic Series • Isoelectronic:having the same number of electrons • N3-, O2-, F-, Ne, Na+, Mg2+, and Al3+ form an isoelectronic series. • A group of atoms or ions that all contain the same number of electrons

  20. Isoelectronic Series • Examples of isoelectronic series: • N3-, O2-, F-, Ne, Na+, Mg2+, Al3+ • Se2-, Br-, Kr, Rb+, Sr2+, Y3+ • Also: Cr, Fe2+, and Co3+

  21. Sizes of Ions - Trends • In an isoelectronic series, ions have the same number of electrons. • Ionic size decreases with an increasing nuclear charge.

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