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Tungsten is a metal with an extremely high density and thermal capacity. Not only does it have the highest melting point of all metals, it also exhibits the greatest mechanical strength, very high stiffness and the smallest thermal expansion coefficient. Temperatures like those on the surface of the sun are required to bring tungsten to a boil (approx. 5,900°C). With a density of 19.28 g/cm³, tungsten is also among the heaviest metals which is why it is used among other things for specific mass balancing. Tungsten takes eighth place in the electrical conductivity ranking. This means it has about 31% of the electrical conductivity of copper.
Tungsten is also a special metal in terms of its chemistry. It is extraordinarily resistant to air exposure at room temperature. Only at high temperatures does it gradually burn, forming tungsten (VI) trioxide (WO3). It is impervious to most acids and bases. Mineral acids, hydrofluoric acid and even nitrohydrochloric acid (aqua regia) only attack the metal slowly. It does however dissolve quickly in a mixture of nitric and hydrofluoric acid.
Molybdenum as a metal is not quite as well known as tungsten. It has a lower melting point but is nevertheless commonly used for the production of illuminants, in the glass industry, for heating elements and in furnace construction. Molybdenum is a 5th period transition metal. The high-strength, tough and hard metal is a glossy, silvery white. It has the highest melting point of all 5th period elements. While it is a very hard metal, it is softer and more ductile than tungsten. Just like its big brother tungsten, it is not attacked by reducing acids (even hydrofluoric acid).
Oxidising acids such as hot, concentrated sulphuric acid, nitric acid or nitrohydrochloric acid (aqua regia) lead to high removal rates. Molybdenum is also not resistant to oxidising molten Alkalis.