# Q14. Ans given as : option b. Q.14. 1 mole of a diatomic element ${X}_{2}$ contains 34 and 40 moles of electrons and neutrons respectively. The isotopic formula of the element is (a) ${}_{34}{}^{74}X$ (b) ${}_{17}{}^{37}X$ (c) ${}_{34}{}^{40}X$ (d) ${}_{20}{}^{40}X$

Dear Student,

If one X2 molecule contains 34 electrons and 40 neutrons, then one atom of X has 17 electrons and 20 neutrons. Assuming that it is electrically neutral, it will also have 17 protons. The isotope has an atomic number of 17 (number of protons), and a mass number of 37 (number of protons + number of neutrons).

So, the isotopic formula of the element will be ${}_{\mathbf{17}}{}^{\mathbf{37}}\mathbf{X}$.

Therefore, option (b) is correct.