Introduction to Ruthenium
Ruthenium (Ru) is a rare transition metal belonging to Group 8 and Period 5 of the periodic table. Its atomic number is 44. It is one of the six platinum-group metals, known for its exceptional hardness, high melting point, and resistance to corrosion. Ruthenium is primarily used as a hardener in alloys with other platinum-group metals, in electrical contacts, and as a catalyst in various chemical reactions. While not mined extensively in India, its applications in advanced electronics, chemical industries, and specialized jewelry alloys are relevant globally and in industrial sectors within India.
Fundamental Atomic Particles of Ruthenium
The atomic structure of an element is defined by the number of protons, neutrons, and electrons it possesses.
Protons
The atomic number (Z) of an element directly corresponds to the number of protons in the nucleus of its atom. For Ruthenium (Ru), the atomic number is 44. Therefore, a Ruthenium atom contains 44 protons.
Electrons
In a neutral atom, the number of electrons orbiting the nucleus is equal to the number of protons. This balance ensures the atom has no net electrical charge. Since a neutral Ruthenium atom has 44 protons, it also contains 44 electrons.
Neutrons
The number of neutrons in an atom can vary, leading to different isotopes of an element. The mass number (A) of an isotope is the sum of its protons and neutrons. The most abundant naturally occurring isotope of Ruthenium is Ruthenium-102 ($^{102}$Ru). To calculate the number of neutrons in Ruthenium-102: Number of neutrons = Mass number (A) - Number of protons (Z) Number of neutrons = 102 - 44 = 58 neutrons. Other isotopes of Ruthenium exist with different numbers of neutrons, but for general purposes, focusing on the most abundant isotope is common.
Electron Configuration of Ruthenium
The electron configuration describes the arrangement of electrons in the atomic orbitals around the nucleus. For Ruthenium, with 44 electrons, the ground state electron configuration is determined by filling the orbitals according to the Aufbau principle, Hund’s rule, and Pauli exclusion principle.
The full electron configuration for Ruthenium is: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1 4d^7$
This can also be written in a condensed form using the noble gas core configuration of Krypton (Kr), which has 36 electrons: $[Kr] 4d^7 5s^1$
It is observed that Ruthenium exhibits an exception to the strict Aufbau filling order, where an electron from the $5s$ orbital moves to the $4d$ orbital, resulting in a $5s^1 4d^7$ configuration instead of the expected $5s^2 4d^6$. This occurs because the $4d^7$ configuration with a half-filled $5s$ orbital ($5s^1$) or an even more stable $4d^8$ configuration (which is often achieved in compounds) provides greater stability to the atom due to orbital interactions and electron-electron repulsion minimization.
Valence Electrons of Ruthenium
Valence electrons are the electrons located in the outermost principal energy level and, for transition metals, also the electrons in incompletely filled d-subshells that can participate in chemical bonding. These electrons are crucial in determining an element’s chemical properties and reactivity.
For Ruthenium, the outermost principal energy level is $n=5$, which contains the $5s^1$ electron. Additionally, the partially filled $4d^7$ subshell in the ($n-1$) shell (where $n=5$) also contains electrons that readily participate in chemical reactions.
Therefore, the valence electrons for Ruthenium are the $5s^1$ electron and the $4d^7$ electrons. Total number of valence electrons = $1 (from 5s) + 7 (from 4d) = \textbf{8 valence electrons}$. These electrons dictate Ruthenium’s ability to form various oxidation states and its catalytic properties.