There are 7 periods on the periodic table, they separate the elements into horizontal rows based on repeating patterns of similarity among the elements of that period.
Elements in the same period have the same number of electron shells, their atomic number increasing by one as you read from left to right.
Period1 is special because it only contains two elements: Hydrogen and Helium.
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Period 1:
Hydrogen and Helium
1
2
Period 2:
8
3
10
Period 3:
8
11
18
Period 4:
18
19
36
Period 5:
18
37
54
Period 6:
32
55
86
Period 7:
32
87
118
Groups
There are 18 groups on the periodic table (shown in vertical columns) all elements of the same group have the same number of valence electrons (the number of electrons in the outermost energy layer of an element) and (excluding transition metals) the same charge.
%%Special Groups:%% Group 3 contains all of the Lanthancides and Actinides and Group 18 contains only Noble Gases.