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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3.3 - Arrangement of Electrons

In section 3.1 we learned that the electrons are located outside the nucleus of the atom in mostly empty space. In this section we will learn that associated with this empty space are many different energy levels. Electrons are organized in such a way such that repulsions between them are minimized. Therefore, they are interdispersed within this space with distinct distances up to 100,000 times away from the nucleus of the atom. Associated with each distinct distance from the nucleus is an energy level.

We will be looking at three models to understand how electrons are arranged inside an atom. Each model will help us gain a better understanding on this complex arrangement. These models are:

  1. The Bohr Model of the Atom (Section 3.3.1)
  2. The Lewis Electron-Dot Formulas of Elements (Section 3.3.2)
  3. The Quantum Mechanical Model of the Atom (Section 3.3.3)

Section 4.6
Arrangement of Electrons in Principal Energy Levels ..p87




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