Substituents monatomic

For several reasons — including the complete breakdown of sample into its substituent elements in the plasma and the use of an unreactive monatomic plasma gas (argon) — background interferences in the resulting mass spectra are of little importance. Since there are no or very few background overlaps with sample ions, very precise measurements of sample ion abundances can be made, which facilitate the determination of precise isotope ratios. 

No conformational dependence (NCD). Groups of this type include monatomic substituents such as hydrogen and the halogens cylindrical substituents such as the ethynyl and cyano groups, and tetracoordinate symmetric top substituents such as the methyl, trifluoromethyl and silyl groups. 

The group axis Is colllnear with the bond Joining substituent X and skeletal group G For monatomic... 

Some degree of relationship between steric effect parameters and volume parameters must be expected. Consider for example monatomic substituents. A single atom, X, may be considered sperical. Its volume is therefore given by the expression for the volume of a sphere. 

Fig. 1. Van der Waals volume of a monatomic substituent. The quantities rv and rc are the van der Waals and covalent radii respectively. The shaded area is cut off from the sphere when a covalent bond forms...

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