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An element with mass number 81 contains \(31.7 \%\) more neutrons as compared to protons. Assign the atomic symbol.
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Verified Answer
Mass number \(=81\), i.e., \(\mathrm{p}+\mathrm{n}=81\)
If protons \(=x\), then neutrons
\(\begin{aligned}
&=x+\frac{31.7}{100} x=1.317 x \\
&\therefore x+1.317 x=81 \\
&\text { or } 2.317 x=81
\end{aligned}\)
or \(2.317 x=81\)
or \(x=\frac{81}{2.317}=35\)
Thus, Protons \(=35\), i.e., atomic no, \(=35\)
Hence, the symbol is \({ }_{35}^{81} \mathrm{Br}\)
If protons \(=x\), then neutrons
\(\begin{aligned}
&=x+\frac{31.7}{100} x=1.317 x \\
&\therefore x+1.317 x=81 \\
&\text { or } 2.317 x=81
\end{aligned}\)
or \(2.317 x=81\)
or \(x=\frac{81}{2.317}=35\)
Thus, Protons \(=35\), i.e., atomic no, \(=35\)
Hence, the symbol is \({ }_{35}^{81} \mathrm{Br}\)
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