What does the group number mean on the periodic table of elements?
Group number:
(a) What are the usual number of valence electrons and valency of group 18 elements of the periodic table?
(b) What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?
what does first and second series mean in mendeleevs periodic table and what does A and B in the groups of mendeleeves periodic table mean??