ORBITAL NOTATION 9/06

  • SHELL (energy level, principle quantum number) – probability cloud location of electrons.
  • SUBLEVEL – a division of a shell, s, p, d, f
  • ORBITAL (not orbit) a pair of electrons with opposite spin.
  • s sublevel – one orbital, MAX 2 electrons.In all shells.
  • p sublevel- three orbitals, MAX 6 electrons. Shell 2 and higher.
  • d sublevel- five orbitals, MAX 10 electrons. Shell 3 and higher.
  • Electrons MUST fill inner sublevelsfirst (ground state). This is called the Aufbau process as demonstrated below.
  • Electrons in the same orbital MUST have opposite magnetic spin (Pauli Exculsion Principle).
  • To fill “p sublevels” you add one electron to each, then go back and add the second until you have assigned all electrons, this is called Hund’s rule and is demonstrated below.

FILLING ORDER FOR FIRST TWO SHELLS.

1s↑↓ 2s↑↓ 2p↑↓↑↓↑↓

EXAMPLE ONE – PREDICT THE GROUND STATE OF CARBON.

  1. Look up the atomic number (PERIODIC TABLE), this will equal the number of electrons in the ground state (however, not in the ionic state)
  2. Look at the notation for electrons under the atomic number.
  3. Begin filling the 1s, then the 2s, then the 2p until you have assigned all electrons.

1- 6C carbon has an atomic number of 6, therefore you must assign 6 electrons for the ground state.

2-Under the atomic number you should see the numbers 2-4, which means there are 2 electrons in the first shell and four in the second shell.

3-Apply the Aufbau process and Hunds rule.

1st electron: 1s↑ 2s 2p______

2ndelectron: 1s↑↓ 2s 2p______

3rdelectron: 1s↑↓ 2s↑ 2p______

4thelectron: 1s↑↓ 2s↑↓ 2p______

5thelectron: 1s↑↓ 2s↑↓ 2p↑_ __ __

6thelectron: 1s↑↓ 2s↑↓ 2p↑ ↑ __

 at this point you have assigned all electrons and are finished, the configuration is

1s2 2s22p4NOTE the superscripts are NOT exponents, they indicate how many electrons are in a sublevel.

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EXAMPLE TWO – PREDICT THE GROUND STATE OF OXYGEN.

  1. Look up the atomic number (PERIODIC TABLE), this will equal the number of electrons in the ground state (however, not in the ionic state)
  2. Look at the notation for electrons under the atomic number.
  3. Begin filling the 1s, then the 2s, then the 2p until you have assigned all electrons.

1- 8Ocarbon has an atomic number of 8, therefore you must assign 6 electrons for the ground state.

2-Under the atomic number you should see the numbers 2-6, which means there are 2 electros in the first shell and six in shell 2.

3-Apply the Aufbau process and Hunds rule.

1st electron: 1s↑ 2s 2p______

2ndelectron: 1s↑↓ 2s 2p______

3rdelectron: 1s↑↓ 2s↑ 2p______

4thelectron: 1s↑↓ 2s↑↓ 2p______

5thelectron: 1s↑↓ 2s↑↓ 2p↑_ __ __

6thelectron: 1s↑↓ 2s↑↓ 2p↑ ↑ __

7th electron: 1s↑↓ 2s↑↓ 2p↑ ↑ ↑

8thelectron: 1s↑↓ 2s↑↓ 2p↑↓↑ ↑

 at this point you have assigned all electrons and are finished, the configuration is

1s2 2s22p4NOTE the superscripts are NOT exponents, they indicate how many electrons are in a sublevel.