Question

A neutral atom of an element has a nucleus with a nuclear charge 13 times and mass 27 times that of hydrogen nucleus. What is the ratio of electrons to protons in its stable positively charged ion?

• A. 27 : 13
• B. 10 : 19
• C. 10 : 13
• D. 10 : 14

Answer 1

Answer: (C)

10 : 13

Let the neutral atom of the element be $X$.

Given, the nuclear charge of $X$ is 13 times that of the hydrogen nucleus.
$\Rightarrow$ Atomic number $=13$

Mass of X is 27 times that of hydrogen nucleus $\Rightarrow$ Mass number $=27$.

Since ${}_{13}{X}^{27},EC=2,8,3$

If X forms stable positively charged ion i.e., $X^{+3}$ (as it has 3 valence electrons in its valence shell)

$X^{+3}\to$ Atomic number $=13-3=10.$ This implies number of electrons $=10$. Number of protons $=13$.

$Ratio=10:13$