Which of the following will have the smallest radius of first orbit (n = 1)?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Doubly ionized lithium
Radius of the first orbit (n = 1) of an atom be determined using Bohr's Radius formula -
$r=\frac{n^2ε_0h^2}{\pi me^2Z}⇒r∝\frac{1}{m}$
Mass of double ionized lithium = 6 ($He^{2+},H,2H$)
∴ Smallest radius is of $He^{2+}$