The radius of the fourth orbit in hydrogen atom is 0.85 nm. Calculate the velocity of the electron in this orbit.

Explanation

To calculate the velocity of the electron in the fourth orbit of a hydrogen atom with a radius of 0.85 nm, we can follow these steps:

### Step 1: Write down the known values
- Orbital number (n) = 4
- Radius (r) = 0.85 nm = 0.85 × 10^(-9) m
- For hydrogen atom, the atomic number (Z) = 1

### Step 2: Use the formula for the velocity of an electron in an orbit
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