How many time the normal electrons of hydrogen atom revolve round the nucleus in one sec? velocity of the electron 

Explanation

Number of revolutions `= ("velocity of the electron")/("circumference of shell")`
For hydrogen electron in `n=1`, Velocity `= 2.18 xx 10 ms^(-1)`
Circumference of shell `= 3.33 xx10^(-10)m `
Number of times the electrons revolves in one sec `= (2.18xx10^(6))/(3.33xx10^(-10))=6.55xx10^(15)s^(-1)`