Life, elements essential for

The elements essential for life can be divided into macroelements (daily requirement > 100 mg) and microelements (daily requirement < 100 mg). The macroelements include the electrolytes sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg), and the nonmetals chlorine (Cl), phosphorus (P), sulfur (S), and iodine (I). 

In Chapter 10 elements were discussed that as a rule tend to be toxic in their various forms. Chapter 11 covers toxic inorganic compounds of elements that are not themselves generally regarded as toxic. These elements include for the most part the lighter nonmetals located in the upper right of the periodic table (Figure 1.3) and exclude the heavy metals. Most of the elements involved in the inorganic compounds discussed in this chapter are those that are essential for life processes. Any division between toxic and nontoxic elements is by nature artificial in that most of the heavy metals have compounds of relatively low toxicity, and there are deadly compounds that contain elements essential for life. 

One of the elements essential for life, sulfur is a constituent of several of the more important toxic inorganic compounds. The common elemental form of yellow crystalline or powdered sulfur, S8, has a low toxicity, although chronic inhalation of it can irritate mucous membranes. 

Figure 21.2. The distribution of elements essential for life in the periodic table.

The chemical elements essential for life. Those most abundant in living systems are shown as purple. Nineteen elements, called the trace elements, are shown as green. 

There are at least 24 elements essential for life (Table 6.3.1). These must be present and available from the environment in order for BU to survive and flourish. Some are present, but not readily... 

Figure 2-1. Elements essential for life (after Williams in [5]).

Elements essential for life are now classified in four groups ... 

Zinc sulfate is very much tied to agricultural use. Zinc is a trace element essential for life. 

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