Principles for building Electron Structure
n (subshell) ^ # of electrons
Aufbau principle: Under normal conditions atoms are in their lowest energy state, the ground
state. In the ground state, electrons are always in their lowest energy orbitals possible, subject to
Pauli's Exclusion principle.
Pauli's Exclusion principle: No two electrons in an atom in its ground state can have the same
four quantum #. Maximum capacity of any orbital is two electrons with opposite spins.
Hund`s Rule: When placing electrons in orbitals of equal energy, the most stable arrangement
(lowest energy ) is the one that gives the highest total spin.
Pay attention to irregular periodic trends.
Elements that are composed as the same electronic configuration but have different atomic
numbers are considered to be isoelectronic ions.
As their size decreases their atomic number increases.
Review of th