Unit #1Unit #2Unit #3Unit #4Unit #5Unit #6Unit #7Unit #8Unit #9Unit #10
spacerUNIT # 3  

spacerof the Atom

spacerAtomic Number - Number of Protons
spacerNumber of Electrons
spacerMass Number - Number of Neutrons
spacer3.2 Isotopes
spacer3.3 Arrangement
spacerof Electrons

spacerThe Bohr Model
spacerBohr Diagram
spacerThe Lewis Electron-dot Symbol
spacerThe Quantum Mechanical Model of the Atom
spacerElectrons in the sublevels

spacer3.4 Electron

spacerFilling Order of the Sublevels

spacerElectron Configuration Notations
spacerElectron Configuration for Atoms of the First 20 Elements
spacerElectron Configuration and the Periodic Table
spacer3.5 Atomic Mass
spacerCalculation of Atomic Mass
spacerCalculate the Atomic Mass of Carbon

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3.4 - Electron Configurations of Atoms

When electrons fill the energy levels, it fills principal energy levels, sublevels, atomic orbitals from lowest energy first. Click here to view the order in which the sublevels are ordered according to energy. Look carefully and you will see:

  1. some 4 sublevel is lower in energy than a 3 sublevel (i.e. 4s is lower in energy than 3d; denoted by * in the energy diagram)
  2. some 5 or 6 sublevel is lower in energy than a 4 sublevel (i.e. 5p and 6s are lower in energy than 4f; denoted by arrows in the energy diagram )

At first glance it appears that the sequence for electrons to fill the atomic orbitals are of random order. Read on to find an easier way to remember the order of atomic orbitals according to energy.

Section 4.8
Arrangement of the Electrons in Sublevels ..p91

Section 4.9
Orbitals ..p97




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