What is the orbit number of the He ion in which electron have speed times the speed of light? — Atomic Structure Chemistry Question

💡 Solution & Explanation

Speed $v = \frac{c}{137} \cdot \frac{Z}{n}$. For He$^+$, $Z=2$. Thus, $\frac{c}{205.67} = \frac{c}{137} \cdot \frac{2}{n} \implies n = \frac{2 \times 205.67}{137} \approx 3$. Therefore, correct answer is C.