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

spacer3.1
Structure
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
spacerConfigura
tions

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

spacerspacerProblems
spacer1 | 2 | 3
   

Unit #3 ATOMIC STRUCTURE

3.4 - Electron Configurations of Atoms

3.4.3 - Electron Configuration for Atoms of the First 20 Elements

When the electrons are arranged in their lowest energy state, the atom is in the ground state. The following table summarizes the ground state electron configuration of the first 20 elements on the periodic table.

NB: the superscripts add up to the atomic number of the atom.

Name Atomic Number Electron Configuration
Period 1
Hydrogen 1 1s1
Helium 2 1s2
Period 2
Lithium 3 1s2 2s1
Beryllium 4 1s2 2s2
Boron 5 1s2 2s22p1
Carbon 6 1s2 2s22p2
Nitrogen 7 1s2 2s22p3
Oxygen 8 1s2 2s22p4
Fluorine 9 1s2 2s22p5
Neon 10 1s2 2s22p6
Period 3
Sodium 11 1s2 2s22p63s1
Magnesium 12 1s2 2s22p63s2
Aluminum 13 1s2 2s22p63s23p1
Silicon

14

1s2 2s22p63s23p2
Phosphorus 15 1s2 2s22p63s23p3
Sulfur 16 1s2 2s22p63s23p4
Chlorine 17 1s2 2s22p63s23p5
Argon 18 1s2 2s22p63s23p6
Period 4
Potassium 19 1s2 2s22p63s23p64s1
Calcium 20 1s2 2s22p63s23p64s2

 

Section 4.8
Arrangement of Electrons in Sublevels ..p95


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