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Protactinium forms mixed binary oxides with various metals. With alkali metals A, the crystals have a chemical formula APaO 3 and perovskite structure; A 3 PaO 4 and distorted rock-salt structure; or A 7 PaO 6, where oxygen atoms form a hexagonal close-packed lattice. In all of these materials, the protactinium ions are octahedrally coordinated.
Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series , which starts with the primordial isotope uranium-235 ; the equilibrium concentration in uranium ore is 46.55 231 Pa per million 235 U.
However, the 231 Pa (with a half-life of 3.27 × 10 4 years) formed via (n,2n) reactions with 232 Th (yielding 231 Th that decays to 231 Pa), while not a transuranic waste, is a major contributor to the long-term radiotoxicity of spent nuclear fuel. While 231 Pa can in principle be converted back to 232
Isotherms of an ideal gas for different temperatures. The curved lines are rectangular hyperbolae of the form y = a/x. They represent the relationship between pressure (on the vertical axis) and volume (on the horizontal axis) for an ideal gas at different temperatures: lines that are farther away from the origin (that is, lines that are nearer to the top right-hand corner of the diagram ...
Theoretical chemistry requires quantities from core physics, such as time, volume, temperature, and pressure.But the highly quantitative nature of physical chemistry, in a more specialized way than core physics, uses molar amounts of substance rather than simply counting numbers; this leads to the specialized definitions in this article.
In physics, there are equations in every field to relate physical quantities to each other and perform calculations. Entire handbooks of equations can only summarize most of the full subject, else are highly specialized within a certain field. Physics is derived of formulae only.
Physical organic chemistry is the study of the relationship between structure and reactivity of organic molecules.More specifically, physical organic chemistry applies the experimental tools of physical chemistry to the study of the structure of organic molecules and provides a theoretical framework that interprets how structure influences both mechanisms and rates of organic reactions.
Physics is also called "the fundamental science" because all branches of natural science including chemistry, astronomy, geology, and biology are constrained by laws of physics. [58] Similarly, chemistry is often called the central science because of its role in linking the physical sciences.