Question

Which of the following elements does not indicate natural Radioactive activity?
1. Aluminium
2. Thorium
3. Polonium
4. Uranium

Answer 1

Correct Answer - Option 1 : Aluminium

The Correct Answer is Aluminium.

• Aluminum is a chemical element with the symbol Al and atomic number 13. 
• Aluminum has a density lower than those of other common metals, at approximately one-third that of steel. 
• It has a great affinity towards oxygen and forms a protective layer of oxide on the surface when exposed to air. 

• Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point.
• Polonium is a chemical element with the symbol Po and atomic number 84. Rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table thallium, lead, and bismuth. 
• Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table.
• A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons.