A hydrogen atom has a diameter of about

9.95 nm.

Express this diameter in meters.

1 meter = 1e9 nm

To get meters, divide nanometers by 1e9:

9.95nm / 1x10^9 = 9.95x10^-9 meters

Answer: 9.95e-9 meters

1 meter = 1,000,000,000 nanometers

OR

1 nanometer = 0.000000001 meters

so, to convert the diameter of a hydrogen atom in nanometers to meters, you just have to multiply

9.95 x 0.000000001 = 0.00000000995 nm

therefore the diameter of a hydrogen atom in meters is 0.00000000995m