Atomic Theory - Electron Configuration

On this page you will be constructing electron configurations of atoms and ions. When you click "New Problem", an atom or ion will appear in the space below. Place the electrons in the appropriate orbitals; follow the rules for electron configuration. To indicate the degree of occupancy of a given orbital, do the following:

• If the orbital has no electrons leave the cell empty. If it has a single electron, enter a 1 in the cell. If it has a pair of electrons, enter a 2 in the cell.
• Anything other than empty, a 1 or a 2 will cause your answer to be ruled incorrect.
• Special cases
  • Half or fully filled d subshells (24 or 29 electrons)such as Cr or Cu must be properly noted. In general, all s¹d⁵(24 electrons) and s¹d¹⁰(29 electrons) configurations will be considered as preferred, provided the species has a charge of 1+ or less. Thus Mn¹⁺ is a special case, but Fe²⁺ is not.
  • For neutrals and anions the 4s fills before the 3d. For cations, the 3d fills first.
• Since this is an exercise in determining electron configurations, no effort has been made to limit the possible species to observed ions. Thus, don't be surprised to see Na^3-.
• Be certain to follow Hund's rule and, for simplicity, fill the orbitals in partially filled subshells from left to right. Thus, if you have 4 electrons in a p subshell, enter them 2 1 1. If you enter other than this, the program will try rearrange your entries according to the above convention.
• If you miss a problem three times, pressing "Show Answer" will display the complete solution and you will no longer be able submit an answer for that problem.