Strontium Oxide Has a Face Centered Cubic Unit Cell of Oxide

Multiple Choice

Strontium oxide has a face centered cubic unit cell of oxide ions with the strontium ions in octahedral holes.If the radius of Sr²⁺ is 127 pm and the radius of O^2- is 135 pm,what is the density of strontium ions oxide? (100 cm = 1 × 10¹² pm)

A) 0.209 g/cm³
B) 1.20 g/cm³
C) 2.39 g/cm³
D) 4 g/cm³
E) 4.78 g/cm³