state modern periodic law ?arrange the element of halogen family in the increasing order of their number of Shell ?what type of Bond formation exists between the element of group 1 and 17 and why?

Modern periodic law states that the properties of elements are dependent on their atomic numbers and elements show similar properties at regular interval of increasing atomic number.

Question 2 :FluorineChlorineBromineIodineAstatine Question 3 :

3. Ionic Bond .

Reason : The elements from Group I are metals ( they lose electrons )

The elements from Group 17 are non-metals ( they Gain electrons

IONIC BONDING: this occurs between metal and nonmetal atoms. It occurs as a result of electron transfer from one atom to another.
           Example: NaCl is an ionic compound (between a metal, Na, and a nonmetal, Cl)

POLAR COVALENT: 2 atoms share bonded pairs of electrons sort of unequally. Electrons in a polar covalent bond are more attracted to one atom than the other atom. This type of bonding occurs between nonmetals.
           Example: HF has polar covalent bonds

NONPOLAR COVALENT: occurs between nonmetals atoms. this type of bonding occurs between atoms with almost the same electronegativity.
           Example: N2