The IUPAC name of an element is Unnilnilium. Its atomic number is            

To give the name of an element with atomic number more than 100, we must follow the IUPAC rules. Let us see the following table

From the table we can determine the atomic number of an element from its name. Here, ‘un’ means 1, ‘nil’ means 0 and again ‘nil’ means 0. Therefore, the atomic number of an element with IUPAC name of an element unnilnilium is 100.