Question

The number of protons, electrons and neutrons in a species are equal to $17,\,18$ and $18$ respectively. Which of the following will be the proper symbol of this species?

• A. ${ }_{17}^{35} C l$
• B. ${ }_{17}^{35} C l^-$
• C. ${ }_{17}^{36} C l$
• D. ${ }_{17}^{36} C l^-$

Answer 1

Answer: (B)

$p=17, e=18, n=18$
means, $Z=17 \Rightarrow $ element is chlorine, which contains one electron more
$(17+1)$, so it is chloride ion, $Cl ^{-}$
$\Rightarrow $ Symbol: ${ }_{17}^{35} Cl ^{-}$
Mass number, $A=n+p=18+17=35$
Atomic number, $Z=17$