Introduction to Tennessine (Ts)
Tennessine (Ts) is a synthetic chemical element with the atomic number 117 and the symbol Ts. It is a superheavy element, meaning it has an atomic number greater than 103, and is not found naturally on Earth. Its synthesis was first reported in 2010 by a collaboration of scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, with significant contributions from laboratories in the United States, including Oak Ridge National Laboratory in Tennessee, after which the element is named. Tennessine is located in Group 17 of the periodic table, placing it among the halogens, although its chemical properties are predicted to deviate from the lighter halogens due to relativistic effects. Due to its extreme instability and very short half-life, its chemical properties have not been directly observed.
Atomic Structure: Protons, Neutrons, and Electrons
The atomic number of an element defines the number of protons in the nucleus of an atom. For Tennessine:
- Atomic Number (Z): 117
- Number of Protons: 117
In a neutral atom, the number of electrons is equal to the number of protons. Therefore, for a neutral Tennessine atom:
- Number of Electrons: 117
The number of neutrons can vary, leading to different isotopes of an element. The most stable known isotope of Tennessine is Tennessine-294 ($\text{Ts}^{294}$), which has a mass number (A) of 294. The mass number is the sum of protons and neutrons in the nucleus.
- Mass Number (A): 294
- Number of Neutrons: Mass Number - Atomic Number = 294 - 117 = 177
Therefore, an atom of neutral Tennessine-294 contains 117 protons, 177 neutrons, and 117 electrons.
Electron Configuration
Electron configuration describes the arrangement of electrons in an atom’s atomic orbitals. For Tennessine, with 117 electrons, the full electron configuration follows the Aufbau principle, filling orbitals in order of increasing energy, and Hund’s rule, which states that orbitals of equal energy are first occupied singly before pairing up.
Given its position as the seventh element in Group 17 and in Period 7, its electron configuration can be expressed using the noble gas core notation, referencing the noble gas from the preceding period, which is Radon (Rn). Radon has 86 electrons.
The electron configuration for a neutral Tennessine atom is:
$\text{[Rn]} \ 5f^{14} \ 6d^{10} \ 7s^2 \ 7p^5$
This notation means that the electron shells up to Radon are filled, followed by the filling of the $5f$ subshell with 14 electrons, the $6d$ subshell with 10 electrons, the $7s$ subshell with 2 electrons, and finally the $7p$ subshell with 5 electrons.
Valence Electrons
Valence electrons are the electrons located in the outermost electron shell of an atom. These are the electrons that are primarily involved in chemical bonding. To identify valence electrons, one looks for the electrons in the highest principal quantum number (n) shell.
For Tennessine, the highest principal quantum number is $n=7$. The electrons in this outermost shell are found in the $7s$ and $7p$ subshells:
- $7s^2$: Contains 2 electrons
- $7p^5$: Contains 5 electrons
Adding these together, Tennessine has a total of 7 valence electrons. This is consistent with its placement in Group 17 of the periodic table, where elements typically exhibit 7 valence electrons, contributing to their characteristic chemical reactivity.