Niobium ( Nb ) and ruthenium (Ru) have "x" and "y" number of electrons in their respective 4 d orbitals The value of x+y is _______.

Electronic Configurations

• Niobium (Nb, $$Z=41$$): Instead of the expected $$[Kr] 4d^3 5s^2$$, the experimental configuration is $$[Kr] 4d^4 5s^1$$
  • Number of electrons in the $$4d$$ orbital ($$x$$) = $$4$$
• Ruthenium (Ru, $$Z=44$$): Instead of the expected $$[Kr] 4d^6 5s^2$$, the experimental configuration is $$[Kr] 4d^7 5s^1$$.
  • Number of electrons in the $$4d$$ orbital ($$y$$) = $$7$$

Calculation

Using the values identified above: $$x + y = 4 + 7 = 11$$

Final Answer: The value of $$x + y$$ is $$11$$.

This exception occurs because the energy gap between the $$4d$$ and $$5s$$ orbitals is very small, allowing for electron shifts that minimize inter-electronic repulsions or provide stability through specific exchange energies.