Question

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

• A. $27:13$
• B. $10:13$
• C. $20:24$
• D. $10:14$

Answer 1

Answer: (B)

$10:13$

Nuclear charge is $13$ times Hydrogen atom. $\therefore$ number of protons$=13$

Mass is $27$ times Hydrogen. $\therefore$ Mass number $=27$

Thus element is ${}_{13}^{27}Al$. The stable positive ion of Al is ${Al}^{3+}$. Thus in ${Al}^{3+}$, there are $13$ protons and $10$ electrons. Hence ratio of electron to proton is $10:13$