Argon (Wikipedia)Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in Earth’s atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth’s crust, comprising 0.00015% of the crust.
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Helen Keller (Wikipedia)Helen Adams Keller (June 27, 1880 – June 1, 1968) was an American author, disability rights advocate, political activist and lecturer. Born in West Tuscumbia, Alabama, she lost her sight and her hearing after a bout of illness when she was 19 months old. She then communicated primarily using home signs until the age of seven, when she met her first teacher and life-long companion Anne Sullivan. Sullivan taught Keller language, including reading and writing. After an education at both specialist and mainstream schools, Keller attended Radcliffe College of Harvard University and became the first deafblind person in the United States to earn a Bachelor of Arts degree.