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.
NaCl (common salt) is an example of an ionic substance. Covalent bonding occurs when atoms share electrons with each other. This gives rise to two types of structures: molecules and covalent network solids. Methane (CH4) is a covalent molecule and glass is a covalent network solid. In molecules we can distinguish individual covalent bonds between pairs of atoms.