Your SlideShare is downloading. ×
How are electrons placed in the atom?
Upcoming SlideShare
Loading in...5

Thanks for flagging this SlideShare!

Oops! An error has occurred.

Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

How are electrons placed in the atom?


Published on

This PowerPoint tells you more about the three principles which we have to follow when filling in electrons in electron-in-box diagrams.

This PowerPoint tells you more about the three principles which we have to follow when filling in electrons in electron-in-box diagrams.

Published in: Education

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

No notes for slide


  • 1. How are electrons placed in the atom?
  • 2.
    • Introduction
      • Everybody knows that there are electrons orbiting atoms, but how are they arranged in the atom? 
      • There are actually a set of rules which govern the placement of electrons. 
      • The rules are called AUFBAU Principle, Pauli Exclusion Principle and Hund's Rule. 
      • However, these rules only apply to the ground state of an atom or ion .
  • 3.
    • AUFBAU Principle
      • The lowest energy levels are always filled first
      • Conversely, electrons are lost from the highest energy levels first 
      • The diagram shows the order in which we should fill up the subshells.
  • 4.
    • Diagram showing different energy levels of various atoms
    Scale/Quantum Number Arrangement of electrons Orbital Elements Subshell
  • 5.
    • Pauli Exclusion Principle
      • If there are 2 electrons occupying the same orbital, the 2 electrons must be of opposite spins so as to stay at ground state
  • 6.
    • Hund's Rule
      • If multiple orbitals of the same energy are available, Hund's rule states that unoccupied orbitals will be filled before occupied orbitals are filled up by electrons having different spins. Element: Carbon
  • 7.
    • Anomalous Electron Configurations
    • Certain atoms do not follow the orbital-filling rules: 
      • Chromium's electron configuration is [Ar]3 d 5 4 s 1 instead of the expected [Ar]3 d 4 4 s 2   if we are to follow the normal rules
      • Copper's electron configuration is [Ar]3 d 10 4 s 1 instead the expected [Ar]3 d 9 4 s 2  
      • There are others in the heavier d -block metals and the f -block metals. Molybdenum and Rhodium are some examples.
    • This occurs when there are enough electrons to produce a half-filled set of degenerate orbitals (as in the case of chromium) or to completely fill a d or f subshell (like copper).
  • 8.
    • The seat a Singaporean would take in a bus.
      • Orbital: A set of two seats beside one another.
      • AUFBAU principle: One would try to be as near the front as possible since it requires lesser energy.
      • Pauli exclusion principle: No 2 people are exactly the same.
      • Hund's Rule: People would rather not to sit next to each other.
      • Subshell: A set of orbitals beyond which the force of attraction towards the front is lower than the force of repulsion from other people, when it is not completely full.