JEE Main 2026 — Apr 4, Shift 2 — Chemistry solution

JEE Main2026Apr 4, Shift 2Chemistry

The species having identical radii according to the Bohr's theory are:

A. H (first orbit)

B. He $^{+}$ (first orbit)

C. He $^{+}$ (second orbit)

D. Li $^{2 +}$ (first orbit)

E. Be $^{3 +}$ (Second orbit)

Choose the correct answer from the options given below:

Solution

Bohr radius: $r_{n} = a_{0} \frac{n ^{2}}{Z}$ , where $a_{0} = 0.529$ Å.

A. H (n=1, Z=1): $r = a_{0}$ .

B. He $^{+}$ (n=1, Z=2): $r = a_{0} /2$ .

C. He $^{+}$ (n=2, Z=2): $r = 4 a_{0} /2 = 2 a_{0}$ .

D. Li $^{2 +}$ (n=1, Z=3): $r = a_{0} /3$ .

E. Be $^{3 +}$ (n=2, Z=4): $r = 4 a_{0} /4 = a_{0}$ .

$∴$ A and E have identical radii ( $= a_{0}$ ).

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