Final answer:
Rhodium, with an atomic number of 45, is the element in the same period as ruthenium with a higher atomic number.
Step-by-step explanation:
The element placed in the same period as ruthenium but with a higher atomic number is rhodium (Rh). Ruthenium has an atomic number of 44, and as we move horizontally across the periodic table, the next element in the same period with a higher atomic number is rhodium, with an atomic number of 45. Both ruthenium and rhodium are part of the transition metals, specifically the platinum group metals, which are known for their resistance to corrosion and stability as cations in water.