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 2.10 mm?

Here we have to get the number of strontium atom needed to be laid side by side to span a distance of 2.10 mm.

9.03×10⁷ number of strontium atoms are needed to cover the distance of 2.10mm.

The radius of the strontium atom is 215 pm, thus the diameter of strontium atom is (2×215) = 430 pm.

Now we know 1 pm is equivalent to 10⁻⁹ mm. Thus 430 pm is equivalent to (430×10⁻⁹) = 4.3×10⁻⁷ mm.

Thus 1 strontium atom can occupy 4.3×10⁻⁷mm of space. Now the distance to be occupied by the lay down of the strontium atom side by side of the span is 2.10 mm.

Hence, ×10⁷ = 9.03×10⁷ number of atoms are needed.

the answer is c.the valence of the atoms combine .