Radius of the fourth orbit in hydrogen atom is 0.85 nm. Calculate the velocity of the electron in this orbit (mass of electron `= 9.1 xx 10^(-31) kg)`.

Explanation

To calculate the velocity of the electron in the fourth orbit of a hydrogen atom, we can follow these steps:

### Step 1: Understand the Formula for Velocity
The velocity \( v \) of an electron in the nth orbit can be derived from the angular momentum postulate of Bohr's model of the atom. The formula is given by:

\[ v = \frac{nH}{2\pi mR} \]
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