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osmium
Science; General science
A chemical element, Os, atomic number 76, atomic weight 190.2. The element is a hard white metal of rare natural occurrence, usually found in nature alloyed with other platinum ...
phosphorus
Science; General science
A chemical element, P, atomic number 15, atomic weight 30.9738. Phosphorus forms the basis of a very large number of compounds, the most important class of which are the ...
protactinium
Science; General science
A chemical element, Pa, atomic number 91. Isotopes of mass numbers 216, 217, and 222–238 are known, all of them radioactive. Only 231 Pa, the parent of actinium, 234 Pa, and ...
lead
Science; General science
A chemical element, Pb, atomic number 82 and atomic weight 207.19. Lead is a heavy metal (specific gravity 11.34 at 16°C or 61°F), of bluish color, which tarnishes to dull gray. ...
palladium
Science; General science
A chemical element, Pd, atomic number 46, and atomic weight 106.4. A transition metal, palladium occurs in combination with platinum (Pt) and is the second most abundant ...
promethium
Science; General science
A chemical element, Pm, atomic number 61. Promethium is the “missing” element of the lanthanide rare-earth series. The atomic weight of the most abundant separated radioisotope is ...
polonium
Science; General science
A chemical element, Po, atomic number 84. Marie Curie discovered the radioisotope 210 Po in pitchblende. This isotope is the penultimate member of the radium decay series. All ...
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