• # question_answer The Bohr's orbit radius for the hydrogen atom (n = 1) is approximately $0.530\,\overset{\text{o}}{\mathop{A}}\,.$The radius for the first excited state (n = 2) orbit is A)  1.08 A                        B)  2.12 AC)       5.24 A             D)       6.36 A

We know that Bohr's radium $=\frac{{{\text{(Number}\,\text{of}\,\text{excityed}\,\text{state)}}^{\text{2}}}}{\text{Atomic}\,\text{number}\,\text{of}\,\text{hydrogen}\,\text{atome}}\,\times \,\text{Radius}\,\text{of}\,\text{hydrogen}\,\text{atom}$ $=\frac{{{(2)}^{2}}}{1\times 0.530}=4\times 0.530=2.120\,\overset{\text{o}}{\mathop{\text{A}}}\,.$ Hence, the correct option is (b).