Each table in the table provides data for a chemical element: symbol, atomic mass, atomic number, element name, electrons in the layers, and whether the element is radioactive.
The horizontal rows are called periods. In them, the chemical elements are arranged in ascending order of their atomic numbers.
The period order number indicates the number of energy levels or electronic layers of the element.
The periodic table presents seven periods:
1st period - 2 elements
2nd period - 8 elements
3rd period - 8 elements
4th period - 18 elements
5th sentence - 18 elements
6th sentence - 32 elements
7th sentence - 32 elements
The vertical columns constitute the families or groups, in which the elements are assembled according to their chemical properties.
Families or groups range from 1 to 18. Some families have names, such as:
1 - alkaline
2 - earth alkaline
13 - boron family
14 - carbon family
15 - nitrogen family
16 - chalcogen family
17 - family of halogens
18 - noble gases
From family 1 and 2 and 13 to 18 we call elements representative.
From the family of 3 to 12 we call elements of transition.
The elements in the lanthanides and actinides series are the elements of transition. Since they are in group 3, as if they were in a "box" into the table, they are called internal transition elements. And the rest are called elements of external transition.