The group number indicates which group the element is in. The main group is composed of short-period elements and long-period elements. The periodic table of elements is divided into seven main groups, seven sub-groups, an eighth group, and a zero group. The main group number = the number of outermost electrons = the highest positive valence = 8-|negative valence| =Number of valence electrons.

Group number

Main group number = number of outermost electrons = highest positive valence = 8- | negative valence | = number of valence electrons

1. Elements whose group number is equal to the period number: H, Be, Al.

2. Elements whose group number is equal to twice the period number: C, S.

3. Elements whose group number is equal to 3 times the period number: O.

4. Elements whose period number is twice the group number: Li.

5. Elements whose period number is three times the group number: Na.

Main group

The main group is represented by Roman numerals followed by A (such as IIA) in the periodic table of chemical elements. Main group elements are a classification of elements in chemistry and refer to the elements in the s and p blocks of the periodic table. Another definition of a main group element is a chemical element in which the number of electrons in the electron shell except the outermost electron shell is full of electrons. Except for transition metals, lanthanides, actinides, and noble gases, all elements in the periodic table are main group elements.