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.
Covalent bonding can produce much larger molecules as well. DNA molecules consist of huge numbers of atoms held together mainly by covalent bonds. But there are other ways to hold atoms together. Ionic bonding As an example of another type of bond, let's consider a sodium atom and a chlorine atom.