Classification of substances in different regions of the CS was based on the presence of particular elements in the formulas of the studied compounds. Organic: We say that a chemical is an organic substance if carbon is part of its composition. Organometallic: All chemicals containing carbon and metals. If a compound is a salt, at least one of the ions must contain C and a metal. As metals, we considered the following elements: Li,Be,Na,Mg,Al,K,Ca,Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Ga,Rb,Sr,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,C d,In,Sn,Cs,Ba,La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Hf,Ta,W,Re,Os,Ir,Pt,Au,Hg ,Tl,Pb,Bi,Po,Ra,Ac,Th,Pa,U,Np,Pu,Am,Cm,Bk,Cf,Es,At,Fr,Fm,Md,No,Lr. REE: all chemicals containing at least one of the following elements Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.