01 Introduction to Chemistry
02 The Structure of Atoms
03 Concept of Mole, Formulae and Equations
04 Periodic Table of Elements
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4.2.1 Arrangement of Electrons in Periodic Table

Periodic Table and Electrons Arrangement​

  1. The classification of Group and Period are totally related to the electron arrangement of the atoms. As shown in the table above, the classification of elements in a periodic table is as follows:
    1. All the elements in the same group have an equal number of valence electron(s) (outer most electron)
    2. All the elements in the same period have an equal number of electron shell(s) (orbit).
  2. For example, the electron arrangement of calcium is It has 2 valence electron and 4 electron shell. Therefore, it is placed in Group 2, period 4.
  3. Hydrogen, the simplest element atom, with 1 electron, does not fit into any group. (Even though some of the periodic table place it in Group 1, due to its 1 (and the only one electron) valence electron.
Number of Valence Electron in a Group
Number of Valence Electron
Group 1
Group 2
Group 13
Group 14
Group 15
Group 16
Group 17
Group 18