The value of Rydberg constant (RH) is 2.18 10-18 J. The velocity of electron having mass 9.1 10-31 kg in Bohr's first orbit of hydrogen atom = 105 ms-1 (nearest integer).
Answer
22
Solution
Bohr's model: speed of the electron in the nth orbit is vn = 2.18 106 Zn m s-1
(this value comes from 12mv2 = RH Z2n2 with the given RH and m)
For the first orbit of H, Z = 1 and n = 1, so
v1 = 2.18 106 m s-1 = 21.8 105 m s-1 22 105 m s-1
Answer: 22