question_answer

\[{{X}^{3-}}\]is isoelectronic with argon. It has electrons and neutrons in 1 : 1 ratio. The mass number of 'X' is (a) 30                                     (b) 32 (c) 33                                     (d) 35

Answer:

\[{{X}^{3}}\]is isoelectronic with argon. \[\Rightarrow \]The number of electrons in\[{{X}^{3}}=18\]. \[\Rightarrow \]The number of protons in\[{{X}^{3}}=\]The number of electrons in neutral atom of \[x=183=15\]. The ratio of electrons to neutrons = 1 : 1 \[\Rightarrow \] The no. of neutrons (n) in \[X=15\]. Mass number (A) of\[X=15+15=30\]