Flerovium (Fl), a superheavy element with atomic number 114, sits at the far reaches of the periodic table. This element is synthetic, meaning it does not occur naturally and must be created in a laboratory, which makes its properties extraordinarily difficult to study directly. Scientists must rely almost entirely on theoretical models and advanced calculations to predict its characteristics, including its density. The predicted density offers a window into the bizarre physics governing the heaviest elements.
The Elusive Element Flerovium
Flerovium is classified as a superheavy element, placing it in the seventh period of the periodic table, directly beneath lead in Group 14. Its existence was confirmed after it was first synthesized in 1998 by a joint team of scientists from the Joint Institute for Nuclear Research in Dubna, Russia, and the Lawrence Livermore National Laboratory in the United States. The process of creating Flerovium involves bombarding a target of \(\text{Plutonium-244}\) with a beam of \(\text{Calcium-48}\) ions in a particle accelerator. This collision produces Flerovium atoms one at a time, making it impossible to collect a macroscopic sample for traditional measurement.
The fundamental reason direct density measurement is unfeasible lies in the element’s fleeting existence. The most stable known isotope, \(\text{Flerovium-289}\), has a half-life of only about 2.1 to 2.6 seconds before it radioactively decays into a lighter element. This minuscule lifespan means that standard physical techniques, which require grams or even milligrams of material, are useless. Consequently, scientists must turn to computational quantum mechanics to model the element’s atomic structure and predict its bulk properties.
The Predicted Density Value and Physical State
Based on sophisticated theoretical modeling, the predicted density of Flerovium in its condensed, solid state is often cited around \(\text{14 g/cm}^3\). This value is an estimate for the element’s density at its melting point. For context, its lighter homologue, lead, has a density of \(\text{11.34 g/cm}^3\), suggesting Flerovium would be a dense metal, though perhaps not as dense as some other heavy elements.
What is particularly surprising about Flerovium is its predicted physical state under normal conditions. Despite being a metal in the same group as lead and tin, Flerovium is expected to be highly volatile, behaving more like a noble gas or a liquid metal near room temperature. Theoretical calculations suggest a remarkably low boiling point, perhaps around \(\text{-60 °C}\) (\(\text{210 K}\)), which is far below that of lead. This unusual volatility implies that Flerovium would likely exist as a metallic vapor or a liquid at standard temperature and pressure.
The expected low density and high volatility are intrinsically linked to the element’s unique electronic structure. If Flerovium were a typical heavy metal, it would form strong metallic bonds, resulting in a high melting point and a very high density. The fact that its theoretical density is only slightly higher than lead and its predicted boiling point is so low confirms that its metallic bonding is surprisingly weak.
The Role of Relativistic Effects in Prediction
The theoretical models used to calculate Flerovium’s density and volatility must account for the effects of special relativity. The Flerovium nucleus contains 114 protons, giving it a massive positive charge that attracts the electrons with immense force. The innermost electrons must move at speeds approaching a significant fraction of the speed of light to remain in orbit around this large nucleus.
This high velocity causes the electrons’ mass to increase, a phenomenon predicted by Einstein’s theory of special relativity. The increase in mass causes the \(s\) and \(\text{p}_{1/2}\) electron orbitals to contract, pulling them closer to the nucleus. This strong contraction and stabilization of the outermost \(s\) and \(\text{p}_{1/2}\) orbitals makes the electrons in the valence shell much less available for forming chemical bonds with neighboring atoms.
The resulting electronic configuration gives Flerovium a “closed-shell” character, which significantly weakens the metallic bonding that would otherwise hold the atoms together in a dense, solid lattice. The weak metallic bonds lead to a larger effective atomic radius and a much lower cohesive energy than expected for a metal in its position on the periodic table. This reduced cohesive force directly translates into the theoretical predictions: a low melting point, high volatility, and a lower overall solid-state density.