this is a guess but
beryllium?
This isotope is 210Po, an alpha emitter with a half life of 138,376 days.
hydrogen is most commonly found as a part of water with oxygen.
Polonium has 33 isotopes, more than any other element, of which all are radioactive.
Polonium
I think it is hydrogen
Polonium with the atomic number 84 is in the group 16 and period 6 of the periodic table of Mendeleev. Some compounds of polonium are: PoO, PoO2, PoO3, PoH2, halides as PoX2, PoX4, PoX6 and the strange class of polonides (compounds of polonium with other metals). The Pauling electronegativity is 2. Possible valences are: 2, 4, 5, 6, -2. Polonium is considered generally as a metal but some chemists consider Po as a metalloid.
Polonium and radium isotopes exist in the decay chains of Th-232, U-233, U-235, U-238.
Polonium is more reactive than plutonium. Polonium is a highly radioactive element and readily reacts with other elements or compounds, while plutonium is also radioactive but less reactive than polonium.
Lead is a naturally occurring element that is primarily created through the decay of heavy radioactive elements, such as uranium and thorium. It can also be formed through the decay of other elements, such as radon and polonium. Lead can be found in various minerals and ores, and is commonly extracted through mining and refining processes.
MMe Marie Curie is credited with two Nobel Prizes and the discovery of Radium and Polonium, the latter named after her native Poland- she was a naturalized French citizen. Some other Female scientist discovered an element in tne thirities but the name escapes me. It might have been Francium ( the element).
The element with an atomic weight of 209.9 is bismuth. It is a post-transition metal that is known for its distinctive pink hue and low toxicity compared to other heavy metals. Bismuth is commonly used in cosmetics, medicines, and alloys.
Boron is a metalloid element, which means it has properties of both metals and nonmetals. It is commonly found in nature as borax and other borate minerals.