Electron Configuration

Introduction to Electron Configuration

It indicates how electrons in an atom of an element are Distributed over its shells, sub-shells and orbitals.
Rules:
  1. Electrons fill orbitals (2 in each orbital) starting with lowest n and moving upwards
  2. No two electrons can fill one orbital with the same spin in order to satisfy (Pauli exclusion principle)
  3. For degenerate orbitals, electrons fill each orbital singly before any orbital gets a second electron (Hund's rule).

Example

Hund's Rules

Types of electronic configuration

  1. Distributing electrons in a diagram (called " Orbital Diagram" )
  2. Summarized electronic distribution
  3. Condensed electronic distribution

Example: Distributing electrons in " Orbital Diagram"

Question: Draw a diagram to illustrate the electronic distribution of a 19K atom.

Solution:
Distribute these 19 electrons in Pairs over the orbitals starting from 1s and upward (see diagram below).
 orbital-k-atom

Example: Summarized Electronic Distribution

Question: Write the electronic distribution of a 19K atom.

Solution:
According to the diagram above, distribution of these 19 electrons can be summarized as follows:
19K: 1s2, 2s2, 2p6, 3s2, 3p6, 4s1

Example: Condensed Electronic Distribution

Question: Write the condensed electronic distribution of a 19K atom.

Solution:
Locate the nearst noble gas and replace its total number of electrons instead of what should be in the summarized distribution,
then leave the rest after that.
19K: 1s2, 2s2, 2p6, 3s2, 3p6, 4s1
19K: [Ar]4s1

condensed-electronic-distribution electronic-configuration-k-atom
Remark:
Ground state configuration of any element is when electrons are normally distributed in their regular orbitals.
Excited state configuration of any element is when electrons are NOT distributed in their regular orbitals

Exercise

Exercise on Finding configuration of an Excited Nitrogen Atom

Check your answers here: Solution to the Exercise on Finding configuration of an Excited Nitrogen Atom



Exercise

Exercise on Finding configuration of Ar Atom

Check your answers here: Solution to the Exercise on Finding configuration of Ar Atom




For more details, please contact me here.
Date of last modification: Summer , 2019