Electron Configurations!

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Electron Configurations!
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Electron configurations describe where the
electrons are in a given atom.

• e- are arranged in up to 7 energy levels
• Lower E levels fill up first (Aufbrau principle)
• E levels have 4 orbitals s,p,d,f
• 2 electrons per orbital (Pauli)

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Hydrogen, for example, has one electron in a
spherical s orbital.

• There is a high probability that the electron is
  somewhere in this cloud, a certain radius from
  the nucleus.

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Therefore, the electron configuration for
hydrogen is1S1

• The S denotes the electron is in the S orbital.
• 1 denotes the electron is in period 1.
• Superscript 1 denotes there is 1 electron in the
  1S orbital.

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The electron configuration for helium is 1S2

• Meaning, there are 2 electrons in the 1S enegy
  level of helium!
• Lithium has 3 electrons
• However an S orbital can only hold a maximum of 2
  electrons
• Therefore Li has 2 1S electrons and 1 2S electron
  1S22S1

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Beryllium is 1S22S2

• Since S orbitals can only hold 2 electrons, the
  5th electron, found in boron creates a new
  orbital, called a p.

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Our next element boron, B has one more electron
than Be.

• Since S orbitals can hold a maximum of 2, the new
  electron creates a new p orbital. This is
  balloon shaped and the orbitals exist in pairs
  along 3 axes, x, y and z in the second shell.

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• Boron is 1S22S22p1
• As each atom adds another electron, into the p
  orbital, the electron goes to 2, 3. 4. 5. and 6
  with Ne. Therefore C is
• 1S22S22p2
• Ne is 1S22S22p6
• Notice the first number is the shell
• the letter is the orbital shape
• the superscript is the number of e-
• Notice how different this looks compared
• to prior models

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• D orbitals are different than s or p

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When we get to the d suborbital,

• d electrons have lower energy than s or p
  electrons
• Therefore Sc has a 3d electron. The d electron is
  in the third energy level
• 1S22S22p63s23p64S23d1

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The Periodic Table has s, p, d, f blocks
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Notice the s, p, d, f electron configs for
valence e-
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• Shortcuts You can write a shortcut to the
  electron configuration by going back to the last
  noble gas, putting it in brackets, and then
  adding the outer shell.
• Example Mg, 1S22S22p63s2 becomes Ne3s2

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Question

• Knowing electron configurations
• Hot or Not?

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Definitely HOT!
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The End