Water has greatest boiling and melting points because strong hydrogen bonds between water molecules (intermolecular force). That is because oxygen has largest electronegativity and smallest atomic radius of all elements in group. Other elements in this group do not form hydrogen bonds and they are gasses in room temperature, water is liquid and their boiling and melting points are lower. Boiling and melting point of hydrides gradually increases from H₂S to H₂Te because of increase of the radius and molecular mass of atoms from sulfur to tellurium, that is why intermolecular force of attraction of molecules increases. <span>
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