Reading from left to right, they are arranged in increasing atomic number (protons ) 

Each period (going across) increases in atomic number 
As you go down a period, they have one more ring of electrons 

As you go down a column, called groups, the elements have the same number of valence electrons, which gives them similar chemical activity 

Metals are on the left, nonmetals on the right and metalloids along the zig-zag line that divides the metals and nonmetals, inert gases on the far right 

In general the elements do get heavier as you increase atomic number, but there are variances
according to there atomic mass,atomic number sometimes there compounds.
The periodic table is an arrangement of the chemical organized on the basis of their atomic numbers.
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