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Category Inorganic  

The subgroup vanadium
Members of this subgroup-vanadium, niobium and tantalum-similar to each other as well as Cr, Mo and W. Vanadium is widely distributed in nature and is about 0.005% of the total number of atoms in the earth`s crust.

The subgroup of arsenic
The content of elements considered subgroups of the earth`s crust is relatively small for a number of arsenic and 1 × 10 -4 %-antimony 5 × 10 -6 %-Bi 2 x 10 -6 % decrease. They occur mainly in the form of sulfur minerals-realgara As 4 S 4 , orpiment As 2 S 3 , antimony shine Sb 2 S 3 and bismuth shine Bi 2 S 3 . All three elements are often contained as impurities in ores to various metals during production they may be isolated as byproducts.

The subgroup bromine
Because of belonging to this subgroup of elements number 85-At astatine-in the Earth`s crust is missing and has been obtained artificially. Since the study were exposed to only very small amounts of it, the properties of this element hardly been studied.

Carbon does not belong to the most common elements in nature-the total number of atoms in the earth`s crust, accounting for only 0.14%. Despite this, the value of carbon is extremely high, since it is the basis for the compounds of all living organisms.

The subgroup selenium
The content of selenium in the earth`s crust is 1 × 10 -50 %, tellurium-1 × 10 -7 %, and polonium-only 2 × 10 -15 %. The latter refers to the least common element in nature.

Final review of the elements
If we compare the various properties of different chemical elements, it turns out that the vast majority of these properties is a periodic function of the positive charge of the nucleus and few linearly depend on it. As can be seen from Fig.

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