Introduction to Oganesson
Oganesson (Og) is a synthetic chemical element with atomic number 118. It is the heaviest element currently known and is located in Group 18 of the periodic table, making it the seventh noble gas. Due to its extreme instability and the minuscule quantities in which it has been synthesized, its properties are largely theoretical and based on predictions from its position in the periodic table. The element was first synthesized in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and officially named in 2016 after Russian nuclear physicist Yuri Oganessian.
Atomic Composition
The most stable known isotope of Oganesson is Oganesson-294 ($^{294}$Og). Understanding its fundamental particles is crucial for comprehending its structure.
Protons
The atomic number (Z) defines an element. For Oganesson, Z = 118. Therefore, each atom of Oganesson contains 118 protons in its nucleus. Protons carry a positive electrical charge, contributing to the overall positive charge of the nucleus.
Neutrons
The number of neutrons in an atom can vary between isotopes of the same element. For the isotope Oganesson-294, the mass number (A) is 294. The number of neutrons is calculated by subtracting the atomic number from the mass number (A - Z). Number of neutrons = 294 - 118 = 176 neutrons. Neutrons are electrically neutral and contribute significantly to the atom’s mass.
Electrons
In a neutral atom, the number of electrons is equal to the number of protons. Therefore, a neutral Oganesson atom contains 118 electrons. These electrons occupy specific energy levels or shells surrounding the nucleus and carry a negative electrical charge, balancing the positive charge of the protons.
Electron Configuration
The electron configuration describes the arrangement of electrons in an atom’s orbitals. For Oganesson, predicting the exact configuration is complex due to relativistic effects, which become significant for very heavy elements. However, based on the Aufbau principle and its position in the periodic table, the predicted ground state electron configuration for Oganesson is:
$[Rn] 5f^{14} 6d^{10} 7s^2 7p^6$
This notation means that the electron arrangement starts with the configuration of Radon (Rn), the noble gas preceding Oganesson, followed by additional electrons in the $5f$, $6d$, $7s$, and $7p$ orbitals.
In a more expanded form, showing all shells from the beginning:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^6 7s^2 5f^{14} 6d^{10} 7p^6$
It is important to note that theoretical calculations suggest that Oganesson might not exhibit typical noble gas behavior due to strong relativistic effects on its electrons, particularly the $7p$ electrons. This could lead to a decreased energy gap between the $7p$ and $8s$ orbitals, potentially making it more reactive than lighter noble gases like Neon or Argon, which are widely used in advertising signs globally and as inert atmospheres in welding, respectively.
Valence Electrons
Valence electrons are the electrons in the outermost electron shell of an atom. These are the electrons primarily involved in chemical bonding and determine an element’s chemical properties. For Oganesson, the outermost principal energy level is $n=7$.
Based on the predicted electron configuration ($[Rn] 5f^{14} 6d^{10} 7s^2 7p^6$), the valence electrons are those in the $7s$ and $7p$ subshells. Number of valence electrons = (electrons in $7s$) + (electrons in $7p$) = 2 + 6 = 8 valence electrons.
This arrangement of 8 valence electrons (a complete octet) is characteristic of noble gases, which typically makes them very stable and unreactive. However, as mentioned, relativistic effects are significant for Oganesson, and while it is predicted to be a noble gas, its chemical inertness might be somewhat diminished compared to its lighter congeners due to these unique properties of superheavy elements. This theoretical behavior sets it apart from more familiar noble gases like those found in the gas mixtures used in fluorescent lighting tubes, illustrating the intriguing complexities at the extreme end of the periodic table.