Pentbiunium (Pbu)
Pentbiunium is the systematic name of the theoretical 521. element in the periodic table with a symbol of Pbu and atomic number of 521. Pentbiunium, also known as element 521, has πεντακόσια είκοσι ένα protons in its nucleus, and πεντακόσια είκοσι ένα electrons in its shells.