Block (periodic table) elements that are commonly recognized as metalloids are in the p-block: boron, silicon, germanium, arsenic, antimony, and tellurium. Metalloids tend to have lower electrical conductivity than metals, yet often higher than nonmetals. They tend to form chemical bonds similarly to nonmetals, but may dissolve in metallic alloys without covalent or ionic bonding. Metalloid additives can improve properties of metallic alloys, sometimes paradoxically to their own apparent properties. Some may give a better electrical conductivity, higher corrosion resistance, ductility, or fluidity in molten state, etc. to the alloy. Boron has many carbon-like properties, but is very rare. It has many uses,
Metalloid (∆H) greater than ~42 kJ/mol are metallic when liquid. Such elements include boron, silicon, germanium, antimony, selenium, and tellurium. Estimated values for ∆H of diatomic astatine are 50 kJ/mol or higher; diatomic iodine, with a ∆H of 41.71, falls just short of the threshold figure. "Like typical metals, it [astatine] is precipitated by hydrogen sulfide even from strongly acid solutions and is displaced in a free form from sulfate solutions; it is deposited on the cathode on electrolysis." Further indications of a tendency for astatine to behave like a (heavy) metal are: "... the formation of pseudohalide compounds ... complexes