The chemical properties of elements are determined by their valence shell electronic configuration.
for example; the group 15 ( nitrogen family ),
The valence shell ( outermost shell ) electronic configuration of is ns2np3 , which clearly shows that all the elements have the tendency to make same kind if bonds with a common element.
That is, consider the hydrates of the group, it is NH3 ( ammonia ),PH3 (phosphine ), AsH3 (arsine ) , SbH3 ( stibine ) etc. They are having the same chemical formula and same type of bond (covalent bond )
The physical properties include melting point, boiling point, density etc.
Here for the same nitrogen family, all elements except nitrogen are solids in room temperature whereas nitrogen is gas.