Rickettsia are gram-positive, rod-shaped bacteria.
Size is magnitude of a quantity, such as length or mass.
Size of standard herbarium sheet is 16.5*28.75cm.
Such substances which have definite size and volume are known as Solids.
The Covalent Radius is measured approximately as radius of an atom’s core which is in contact with the core of an adjacent atom. the van der Waals radius represents the over all size of the atom which includes it valence shell.