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Electron Configurations

Discover the Quantum Mechanical Model of the Atom, Electron Configurations, and Configuration Rules. Learn how to use the Periodic Table to determine electron structures and noble gas notations easily.

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Electron Configurations

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  1. Electron Configurations

  2. New Model of the Atom • 1926 – further refined Bohr’s model of the atom by developing the quantum mechanical model

  3. Comparison to Bohr’s Model Electrons in levels Level Max # e- 1 2 2 8 3 18 P+ and n0 in nucleus Gives probability of finding an electron in an area Levels are broken into sublevels Defines exact location of electron

  4. Electron Configurations • Electron configuration – the arrangement of electrons in levels and sublevels • There are 4 sublevels – s p d and f. • Each sublevel can be further broken down into orbitals that each hold 2 electrons.

  5. Electron Configuration Rules • There are 3 rules that explain how electrons occupy levels, sublevels, and orbitals. • Aufbau principle • Pauli exclusion principle • Hund’s rule

  6. Aufbau Principle • An electron occupies the lowest-energy sublevel that can receive it.

  7. Period number Period number - 1 Period number Period number - 2 How to Remember Order

  8. How to Use Periodic Table • Start at top left of periodic table. • Work your way left to right. • As you finish a row, move down. • Remember the d sublevel’s number is one behind the period. • Remember the f sublevel’s number is two behind the period. • 4f follows 6s and 5f follows 7s.

  9. How to Use Periodic Table, continued • Write the level and sublevel filled followed by a superscript to indicate the number of electrons in that sublevel. • s holds maximum of 2 • p holds maximum of 6 • d holds maximum of 10 • f holds maximum of 14

  10. Electron Configurations 3d7 Number of electrons in the sublevel Energy Level Sublevel 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14…etc.

  11. OVERLAPSWhy are d and f orbitals always in lower energy levels? • d and f orbitals require LARGE amounts of energy to create. • According to the Aufbau principle we must skip a sublevel that requires a large amount of energy (d and f orbtials) for one in a higher level but lower energy FOLLOW THE PERIODIC TABLE IN ORDER!

  12. Let’s Try It! • Write the electron configuration for the following elements: H Li N Ne K Zn Pb

  13. Let’s Try It! • Write the electron configuration for the following elements: H 1s1 Li 1s2 2s1 N 1s2 2s2 2p3 Ne 1s2 2s2 2p6 K 1s2 2s2 2p6 3s2 3p6 4s1 Zn 1s2 2s2 2p6 3s2 3p6 4s2 3d10 Pb 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p2

  14. YOU TRY THESE! • Write the electron configuration for the following elements: He Mg O P S Fe Ag

  15. YOU TRY THESE! Answers • Write the electron configuration for the following elements: He 1s2 Mg 1s2 2s2 2p6 3s2 O 1s2 2s2 2p4 P 1s2 2s2 2p6 3s2 3p3 S 1s2 2s2 2p6 3s2 3p4 Fe 1s2 2s2 2p6 3s2 3p6 4s2 3d6 Ag 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d9

  16. Noble Gas Notation • A way of abbreviating long electron configurations • Since we are only concerned about the outermost electrons, we can skip to places we know are completely full (noble gases), and then finish the configuration

  17. Noble Gas Notation • Step 1: Find the closest noble gas to the atom, WITHOUT GOING OVER the number of electrons in the atom. Write the noble gas in brackets [ ]. • Step 2: Find where to resume by finding the next energy level (row in periodic table). • Step 3: Resume the configuration starting with ns2where n is the next level

  18. Noble Gas Notation • Chlorine • Longhand is 1s2 2s2 2p6 3s2 3p5 You can abbreviate the first 10 electrons with a noble gas, Neon. [Ne] replaces 1s2 2s2 2p6 The next energy level after Neon is 3 So you start at level 3 on the periodic table and continue with 3s and 3p until you arrive at chlorine. [Ne] 3s2 3p5

  19. Practice Noble Gas Notation • Write the noble gas notation for each of the following atoms: Cl K Ca I Bi

  20. Practice Noble Gas Notation • Write the noble gas notation for each of the following atoms: Cl [Ne]3s2 3p5 K [Ar]4s1 Ca [Ar]4s2 I [Kr]5s2 4d10 5p5 Bi [Xe]6s2 4f14 5d10 6p3

  21. You Try These • Write the noble gas notation for each of the following atoms. He Mg O P S Fe Ag

  22. You Try These • Write the noble gas notation for each of the following atoms. He 1s2 Mg [Ne] 3s2 O [He] 2s2 2p4 P [Ne]3s2 3p3 S [Ne] 3s2 3p4 Fe [Ar]4s2 3d6 Ag [Kr]5s2 4d9

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