Note that there are now several types of treatments and medical providers for which Medicare Part B pays 100% of the approved charges rather than the usual 80%. These categories of care include home health care, clinical laboratory services, and flu and pneumonia vaccines.
A giant covalent structure is a three dimensional structure of atoms held together (obviously) by Covalent bonds. These atoms are often all the same-so the elements Silicon and Carbon in the allotropes Diamond and Graphite are Giant Covalent structures.
There are four main categories of crystals, as grouped by their chemical and physical properties 1  : Covalent Crystals. 2  A covalent crystals has true covalent bonds between all of the atoms in the crystal. 3  You can think of a covalent crystal as one big molecule. 4  Many covalent crystals have extremely high melting points.