When an osteoblast becomes completely surrounded by its own matrix secretions it is referred to as an

When an osteoblast becomes completely surrounded by its own matrix secretions it is referred to as an osteocyte.
Osteocyte is a type of bone cell, and as the sentence above says, it is formed when osteblast (which creates the substance of bone) gets surrounded by the material it has secreted on its own.

Talc (french chalk) is the ingredient

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.