Chemistry

Concept Basics

// Structure of the periodic table

Learning outcome
Identify orbital sets and differentiate between core and valence electrons

Worked example

Which sets of orbitals are filled and which sets are partially filled in the following neutral atoms (a) Al (b) Cl (c) V (d) As (e) Kr?

Recall from above that s orbitals can accommodate a maximum of 2 electrons, p orbitals 6 electrons, d orbitals 10 electrons, and f orbitals 14 electrons. Therefore, knowing the atomic number of the elements allows us to write the electron configurations.

  1. Al : Z = 13 : 1s full (2), 2s full (2), 2p full (6), 3s full (2), 3p partially full (1).
  2. Cl : Z = 17 : 1s full (2), 2s full (2), 2p full (6), 3s full (2), 3p partially full (5).
  3. V : Z = 23 : 1s full (2), 2s full (2), 2p full (6), 3s full (2), 3p full (6), 4s full (2), 3d partially full (3).
  4. As : Z = 33 : 1s full (2), 2s full (2), 2p full (6), 3s full (2), 3p full (6), 4s full (2), 3d full (10), 4p partially full (3).
  5. Kr : Z = 36 : 1s full (2), 2s full (2), 2p full (6), 3s full (2), 3p full (6), 4s full (2), 3d full (10), 4p full (6)
    [Note, that all shells and sub-shells are full, which is characteristic of Group 18 elements.]
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