In 16 group element, sulphur, selenium and tellurium are respectively: A. Insulator, Semiconductors and Semiconductor B. Semiconductors, Insulators and Insulator C. Insulator, Insulator and Semiconductor D. Semiconductors, Insulator and Semiconductor
Hint: We know that, modern periodic table has eighteen groups and seven periods. Elements present in the 16th group of modern periodic table are oxygen, sulphur, tellurium, selenium and polonium. Another name of this group is group of chalcogens.
Complete answer: > Now, we discuss the conductivity of sulphur, selenium and tellurium. We know that conductivity of a metal is due to movement of ions. Sulphur is a non-metal and we know non-metals are bad conductors of heat and electricity. Electrons of sulphur held very tightly and thus their movement is not possible. So, sulphur is an insulator. > Now, we discuss semiconductors. Semiconductors are the substances whose conductivity is between insulator and conductor. Selenium is a semiconductor and therefore it is used in production of rectifiers (devices that convert AC to DC). > Now, we discuss tellurium. Tellurium is a semiconductor which shows more electrical conductivity in specific directions on the basis of alignment of atoms and also its conductivity increases slightly on exposure to light. When tellurium is in molten state, it is corrosive to iron, copper, etc. Therefore, sulphur is an insulator and selenium and tellurium both are insulators.
Hence, option A is correct.
Note: It is to be noted that, on moving down the group electrical conductivity increases because of increase of atomic radius. Larger the atom, weaker the attraction of nucleus to electrons and this results in free movement of electrons and we know conductivity is due to movement of electrons.