Period 6 element living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life. Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an "estimated" average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. The free element has the third-highest melting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper ore's extraction and refinement. Rhenium
Period 4 element quickly begins to tarnish as it reacts with air. It is soft enough to be cut with a knife and it is the second least dense element. Potassium has a relatively low melting point; it will melt just by putting it under a small open flame. It also is less dense than water, and can, in turn, float. Calcium (Ca) is the second element in period 4, between potassium and scandium. An alkali earth metal, calcium is almost never found in nature due to its high reactivity with water. It has one of the most widely known and acknowledged biological