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The Arrangement of the Periodic Table of Elements

The Periodic Table of the Elements is arranged in order of increasing atomic number (number of protons) of the elements.

1. The horizontal rows of the periodic table are called periods (or rows) 

• The number of the period is the same as the outermost principle energy level. 

2. The vertical columns are called groups or families. 

• The elements in a group exhibit similar properties, due to the same number of valence electrons.

link to the Periodic Trends Atomic Radii

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