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An element with mass number `81` contains `31.7%` more neutrons as compared to protons. Write the symbol for the isotope in the standard fromat. Strategy: Let us assume that the number of protons `=p`. Then, Number of neutrons `(n) = p +31.7%`of `p` |
Answer» Mass number `=` Number of protons `+` Number of neutrons `81=p +n` or `p+(p+(31.7)/(100)xxp)=81` `p+(p +0.317p) = 81` `p+p(1+0.317) = 81` `p+1.317p = 81` `(1+1.317)p = 81` `2.317 p = 81` `p = (81)/(2.317) 34.95~= 35` According to the periodic table, the element with atomic number `35` is bromine, Br. Therefore, the symbol is `_(35)^(81)Br`. |
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