The species having identical radii according to the Bohr's theory are : Choose the correct answer from the options given below :
- A and C Only
- A and E Only
- B and E Only
- C and D Only
Answer
(2) A and E Only
Solution
Radius of the nth Bohr orbit: rn = 0.529 n2Z Å
A. H: n = 1, Z = 1 ⇒ r = 0.529 × 11 = 0.529 Å
B. He+: n = 1, Z = 2 ⇒ r = 0.529 × 12 = 0.265 Å
C. He+: n = 2, Z = 2 ⇒ r = 0.529 × 42 = 1.058 Å
D. Li2+: n = 1, Z = 3 ⇒ r = 0.529 × 13 = 0.176 Å
E. Be3+: n = 2, Z = 4 ⇒ r = 0.529 × 44 = 0.529 Å
∴ A and E have identical radii ( n2Z = 1 for both)
Answer: (2)