Is the water of hydration covalently bound to the compound?

Explain in detail of the four major scientific developments that spurred the formulation of the plate tectonics theory

Identify the lewis acid in this balanced equation: ag+ + 2nh3 -> ag(nh3)2+a. ag+b. nh3c. ag(nh3)2+

Quickly what are the following of organisms that existed over a wide area but only for a limited time period called a.soft fossils b.mold fossils c.index fossils d.trace fossils