25. Refer to the periodic table and select the symbol of the element that fits each of the following descriptions. (a) the semimetal in the second period (b) the semimetal in the fourth period and Group IVA/14 (c) the halogen that exists as yellow gas (d) the halogen that is radioactive 27. Refer to the periodic table and select the symbol of the element that fits each of the following descriptions. (a) the third-period alkali metal (b) the third-period alkaline earth metal (c) the rare earth element with the highest atomic mass (d) the lanthanide that is radioactive