Introduction to Fermium
Fermium (Fm) is a synthetic transuranic element, meaning it is not found naturally on Earth but is produced artificially in laboratories or nuclear reactors. It was discovered in 1952 in the debris of the first hydrogen bomb test. All isotopes of Fermium are radioactive, with the most stable isotope, Fermium-257, having a half-life of about 100 days. Due to its short half-life and the difficulty of its production, Fermium currently has no practical applications outside of scientific research.
Basic Atomic Properties
Fermium is classified as an actinide, which is a series of metallic chemical elements with atomic numbers from 89 (Actinium) to 103 (Lawrencium). These elements are characterized by the filling of their 5f electron shells.
Protons, Neutrons, and Electrons
The atomic number of Fermium is 100.
- Protons: In a neutral atom of Fermium, there are 100 protons. The atomic number directly indicates the number of protons in the nucleus.
- Electrons: For a neutral atom, the number of electrons is equal to the number of protons. Therefore, a neutral Fermium atom has 100 electrons.
- Neutrons: The most stable and common isotope of Fermium for discussion at this level is Fermium-257 ($^{257}$Fm). The mass number (A) for this isotope is 257. The number of neutrons is calculated by subtracting the atomic number (Z) from the mass number (A): Number of neutrons = A - Z = 257 - 100 = 157 neutrons.
Electron Configuration
The electron configuration describes the arrangement of electrons in an atom’s atomic orbitals. For Fermium, determining the full configuration requires understanding the filling order of orbitals for heavy elements.
Simplified Electron Configuration
Using the noble gas notation, the electron configuration of Fermium (Z=100) is based on the noble gas Radon (Rn), which has an atomic number of 86. After the Radon core, the remaining 14 electrons occupy the 5f and 7s orbitals.
The ground state electron configuration of Fermium is: $[Rn] 5f^{12} 7s^2$
This configuration indicates that after the electron configuration of Radon, there are 12 electrons in the 5f subshell and 2 electrons in the 7s subshell.
Valence Electrons
Valence electrons are the electrons in the outermost shell or energy level of an atom, which are involved in chemical bonding. For transition metals and inner transition metals like actinides, the definition can be more complex as inner d or f electrons can also participate.
For Fermium, the valence electrons include those in the outermost 7s orbital and the partially filled 5f orbital. Therefore, the number of valence electrons for Fermium is considered to be 14 (12 electrons from the 5f subshell and 2 electrons from the 7s subshell). These electrons are primarily responsible for any potential chemical interactions of Fermium, though due to its radioactivity and scarcity, its chemistry is primarily studied at trace levels.