Molybdenum has six valence electrons. The atomic number of molybdenum is 42, and its electron configuration is 1s22s22p63s23p63d104s24p64d55s1 or 2, 8, 18, 13, 1 electrons per shell. The electrons in the 4d55s1 constitute its valence electrons.
The symbol for molybdenum is Mo. It is classified as a transition metal and placed in group 6 or d-block and period 5 of the periodic table of elements. Its atomic mass is 95.96 grams per mole, and it has a density of 10.2 grams per centimeter cubed. It is a solid at room temperature and melts at 4,753 degrees Fahrenheit. Molybdenum was discovered by Carl Scheele in 1778 and later isolated by Peter Hjelm in 1781.