The crystal system having the highest and the lowest symmetries respectively , are

The crystal having highest melting point is

The crystal system having one 6 fold axis is

The crystal system having rectangular prisms is

Which of the following given crystal system is the most symmetrical and the most unsymmetrical system respectively?

Among the elements of group 14, the element having highest and that with lowest melting point are respectively.

The elements with the highest and lowest enthalpy of atomisation , respectively for first row transition elements are

The crystal system without any element of symmetry is