atomic number 91
Definition
Noun: A short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead. This is the chemical element with the atomic number 91, known as protactinium.
Usage
The term "atomic number 91" is used in scientific contexts, particularly in chemistry and physics, to identify the specific element protactinium by its number of protons. It is a precise, technical identifier.
Examples
- In the periodic table, atomic number 91 is positioned between thorium and uranium.
- The isotope atomic number 91, protactinium-231, has a half-life of about 32,760 years.
- Scientists studying decay chains track the transformation of uranium into atomic number 91.
Advanced Usage
- The phrase is often used in the format "the element with atomic number 91" for clarity in formal writing.
- In nuclear chemistry, the decay series showing the production of atomic number 91 from uranium-235 is a standard subject of study.
Variants and Related Words
- Protactinium (Pa): The common name for the element with atomic number 91.
- Eka-tantalum: A historical name used by Dmitri Mendeleev in his predictions for the periodic table, referring to the element we now know as atomic number 91.
Synonyms
- Protactinium
- Pa (chemical symbol)
Notes on Meaning
This term has a single, specific scientific meaning. It refers exclusively to the element protactinium and is defined by its fixed position in the periodic table, which is determined by its 91 protons.
Noun
-
a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead
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