Question

The radius fo an atom of Kr si about 1.9 A (w/the tiny circle on top of 'A').
(a) How many Kr atoms would have to be lined up to span 1.0mm?
(b) If the atom is assumed to be a sphere, what's the volume in cm^3 of a single Kr atom?

Answer 1

You need to find diametr first:

1.9 A in radius = 3.9 A in diameter.

A = 1 X 10⁻¹⁰ meters

1.0 mm = 0.001 meters

A) 1.0 mm * (1 m / 1000 mm) * (1×10¹⁰ A / m) * (1 atom / 3.8 A) = 2.6*10⁶ atoms.

B) V = 4/3 * π * r³ = 4/3 * 3.1416 * (1.9 A)³ * (1 m / 10¹⁰ A)³ * (100 cm / 1 m)³ = 2.9*10⁻²³ cm³