Compute the radius r of an impurity atom that will just fit into an fcc octahedral site in terms of the atomic radius r of the host atom (without introducing lattice strains).

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

I’ve been stuck on this for a while

The flow of electrons from one atom to another is called