An element with mass number 81 contains 31.7 % more neutrons as compared to protons. Find the symbol of the atom

Question

An element with mass number 81 contains 31.7 % more neutrons as compared to protons. Find the symbol of the atom (A) 8134Se (B) 8135Br (C) 8136Kr (D) 8137Rb

Tardigrade Admin · Accepted Answer

Mass number of the element = 81 i.e., p + n = 81 Let the number of protons be x. Number of neutrons =x+(31.7/100) × x x=1.317 x ∴ x + 1.317x = 81 or 2.317⋅ = 81 or x=(81/2.317) =34.958 ≈ 35 Symbol of the element =8135Br

Q. An element with mass number $81$ contains $31.7%$ more neutrons as compared to protons. Find the symbol of the atom

$_{34}^{81} S e$

$_{35}^{81} B r$

$_{36}^{81} Kr$

$_{37}^{81} R b$

Mass number of the element $= 81$
i.e., $p + n = 81$
Let the number of protons be $x$ .
Number of neutrons $= x + \frac{31.7}{100} \times x$
$x = 1.317 x$
$∴ x + 1.317 x = 81$ or $2.317 \cdot = 81$
or $x = \frac{81}{2.317}$
$= 34.958 \approx 35$
Symbol of the element $=_{35}^{81} B r$

Q. An element with mass number 81 contains 31.7% more neutrons as compared to protons. Find the symbol of the atom

3481​Se

3581​Br

3681​Kr

3781​Rb