Which two elements should have exactly two unpaired 4d electrons?

Question

Which two elements should have exactly two unpaired 4d electrons?

Answer 1

The 4d subshell begins in period 5 and the first 2 electrons will be unpaired (Hund's Rule). That would be zirconium (Zr).

The next 6 electrons would then leave 2 unpaired 4d electrons. This would be palladium (Pd).