Near 75% of all known chemical elements are metals. Among them there is a series of biologically active macro- and micronutrients (see Table 19).
Table 19. Characteristics of main bioactive metals
Element
Period
Group
Possible Oxidation numbers
Chemical properties
Mg
2A
0, +2
Weak amphoteric metal
K
1A
0, +1
Typical alkali metal
Ca
2A
0, +2
Alkali-Earth Metal
Mn
7B
0, +2, +3, +4, +5, +7
Transition metal
Fe
8B
0, +2, +3, +6
Transition metal
Co
8B
0, +2, +3, +6
Transition metal
Cu
1B
0, +1, +2
Transition metal
Zn
2B
0, +2
Transition metal
Al
3A
0, +1, +3
Amphoteric metal
All bioactive metals depending on its function for plant, animals or human body may be divided into macro-, micronutrients and toxicants (see Table 20).
Table 20. Characteristic of biological function
Element
Biological function
Mg
Included in Chlorophilium
K
Macronutrient for plant nutrition, needed for cell water balance and transparency of membranes
Ca
Macronutrient for plant and human nutrition, takes part in synthesis of proteins
Mn
Micronutrient, takes part in Redox processes. In excess - toxicant
Fe
Micronutrient, needed for processes of breathing and photosynthesis; includes in hemoglobin
Co
Micronutrient, included coferments (for example Vitamin B12 - cobalt ammine). In excess - toxicant
Cu
Irreplaceable micronutrient. In excess - toxicant
Zn
Micronutrient. In excess - toxicant
It is important to know the principles of interaction of metals with different types of acids (see Table 21).
Table 21. Interaction acids-oxidizing agents with metals
Formula of acid
Metals
Notes
Active: The Alkali, The Alkali-Earth, Mg, Zn
Heavy with low activity
Scheme of products
H2SO4 (conc.)
Sulfate + S + H2O
or
Sulfate + H2S + H2O
Sulfate + SO2 + H2O
Fe is immunized by acid
HNO3 (conc.)
Nitrate + N2O + H2O
Nitrate + NO2 + H2O
Not reacts with Au, Pt, Rh, Ir, Ti, Ta;
Al, Fe, Co, Ni, Cr are immunized by acid
HNO3 (diluted)
Nitrate + N2 + H2O
or
Nitrate + NH4NO3+ H2O
Nitrate + NO + H2O
Fe and Sn forms NH4NO3
PRACTICE PROBLEMS
1. Characterize general features of metals atoms.
2. Draw the diagrams of electron redistribution and put the coefficients in the equations of the following reactions and characterize metal properties in these reactions:
Ca + H2O →
Mn + H2SO4 (conc.) →
Zn + CuSO4 →
Al + Fe2O3 →
LABORATORY TRAINING
Experiment 1. Replacing of metals
Put into two test tubes 5-6 drops of CuSO4 and Pb (CH3COO) 2 solutions and add in each tube one granule of free Zinc. 5-10 min. later register how color of Zinc granule is changed. Write the reactions.
Experiment 2. Qualitative test of K+ in salts or fertilizers
Fill test-tube with 3-4 drops of Potassium salt solution and add 2-3 drops of Na3[Co(NO2)6]. Form yellow precipitate NaK2[Co(NO2)6]. Write the reactions of precipitate formation.
Experiment 3.Change of Calcium Phosphates solubility
Add 2-3 drops of Na2HPO4 solution to 1-2 drops of CaCl2 Solution. Why was precipitate formed?
Add by drops Solution of Phosphorus acid to precipitate until to total dissolving. Write the reactions of precipitate formation and dissolving.
Experiment 4. Oxidizing property of Cu+2 ions
Add 2-3 drops of KI solution to 3-4 drops of CuSO4 solution. Observe formation of CuI precipitate and Iodine I2 isolation. Write the reaction.