The radius of a strontium atom is 215 pm. How many strontium atoms would have to be laid side by side to span a distance of 4.19 mm?

0.97 * 10⁹ strontium atoms

Explanation:

if 1 pm is equal with 10⁻⁹ mm

then 215 pm are equal to X mm

X = (215 * 10⁻⁹) / 1 = 215 * 10⁻⁹ mm

Now the diameter of the strontium atom is twice the radius:

diameter = 215 * 10⁻⁹ * 2 = 430 * 10⁻⁹ mm

if 1 strontium atom have a diameter of 430 * 10⁻⁹ mm

then X strontium atom are needed to be laid said by side to span a distance of 419 mm

X = (419 * 1) / (430 * 10⁻⁹) mm = 0.97 * 10⁹ strontium atoms