NEET2015PhysicsAtomic PhysicsActual
Consider third orbit of He + (helium), using non-relativistic approach, the speed of electron in this orbit will be given constant K =9×10 9 , Z =2 and h (Planck's Constant) = 6 .6  ×  10 − 34  J s
Options
- A2.92 × 10 6   m   s - 1
- B1.46 × 10 6   m   s - 1
- C0.73 × 10 6   m   s - 1
- D3.0 × 10 8   m   s - 1
Correct answer
B. 1.46 × 10 6   m   s - 1
Step-by-step solution
Energy of electron H e + E_n = - 13.6 Z 2 n 2   eV ;   Z = 2 ,   n = 3 E 3 =   - 13.6   2 3 2 × 1.6 × 10 - 19   J In Bohr's model energy, E = -   K E E 3 = - K E 3 ∴   9.7 × 10 - 19 = 1 2 m v 2 v =   2 × 9.7 × 10 - 19 9.1 × 10 - 31 Velocity of electron in third orbit of H e + is 1.46 × 10 6   m   s - 1 .