39. ELEMENTS OF SUBGROUP OF ZINC.

 

Atomic number	Name	Electronic configuration	Atomic radius, nanometer	ρ g/cm3	t0pl. 0C	t0kip. 0C	EO	Degrees oxidations
30	Zn zinc	[Ar]3d104s2	0,132	7,13	419,4	907	1,6	+2
48	CD cadmium	[Kr]4d105s2	0,148	8,64	320,9	767	1,7	+2
80	Hg mercury	[Xe]4f145d106s2	0,15	13,59	- 38,8	357	1,9	+1,+2

Physical properties

- Similarity of elements of the main and collateral subgroups in the II group is more, than in the I group.
- Values of density of r and atomic volume increase with increase in atomic mass.

 

Chemical properties

- Reactivity decreases with increase in atomic mass (in the main subgroup – on the contrary).

- Good kompleksoobrazovatel (unlike elements of the main subgroup).         

 

Zinc and its connections

Zinc - metal of silver-white color. In connections shows only one oxidation level +2; compounds of zinc are uncolored.
Normal reduction oxidation potential  ⁺ / is equal to Zn in acidic environment ^{of the Zn2 system} -0,76 in, and     is equal in alkaline condition _{of the ZnO22-/Zn system} to-1,22 century.  Therefore zinc is dissolved in  diluted acids and alkalis

Zn + _{2HCl ZnCl2} + _H2
Zn + _H2SO4 (разб) _ZnSO4 + _H2
Zn + 2NaOH + _{2H2O Na2 of [Zn (OH) 4]} + _H2

Zinc does not decompose water since in aqueous solution it quickly becomes covered by protective film of oxide which protects it from corrosion.
Zinc - strong reducer also forces out less active metals (standing on the right among tension) from solutions of their salts

Zn + _{CuSO4 ZnSO4} + Cu

Zinc oxide shows amphoteric character, being dissolved both in acids, and in solutions of alkalis:

ZnO + _{H2SO4 ZnSO4} + H2O
ZnO + 2NaOH + _{H2O Na2 [Zn(OH)4]}

When heating complex tetrahydroxyzincate-anion is dehydrated:

[_{Zn (OH) 4]2-ZnO22-}+ _2H2O

 Zinc hydroxide  also shows amphoteric properties. It is water-insoluble, but is dissolved in acids and alkalis;

_Zn(OH)2 + 2HCl _ZnCl2 + _2H2O
Zn(OH)2 + 2NaOH _{Na2 [Zn(OH)4]}

Ion of Zn2 + is vigorous kompleksoobrazovatel with coordination number 4. Unlike aluminum hydroxide zinc hydroxide is dissolved in aqueous solution of ammonia:

_Zn(OH)2 + _2NH3 [_{Zn(NH3)4](OH)2}

Cadmium and its connections

 

Cadmium - white, brilliant, soft, ductile metal; it is very little dissolved in inoxidizable acids, well dissolved in the diluted _HNO3 (normal potential ^{of CD/CD 2+} =-0,40 in).
Cadmium forms only one series of compounds where it двухвалентен. ^{CD 2+} ion - is colourless.
 SDO cadmium oxide (brown color) and _{CD cadmium hydroxide (ON) 2} (white color) show the main character, being dissolved only in acids.

CdO + 2HCl _CdCl2 + _H2O

Cd _(OH)2 + 2HCl _CdCl2 + _2H2O

Cadmium is good kompleksoobrazovatel (coordination number 4). Cadmium hydroxide is dissolved in aqueous solution of ammonia:

Cd _(OH)2 + _4NH3 [_{CD (NH3)4](OH)2}

Mercury and its connections

 

Mercury - silver-white, brilliant, the only metal, liquid at the room temperature; has low conductivity (it makes 1,7% of conductivity of silver) and big coefficient of thermal expansion. On air shows stability. Reacts with sulfur and halogens:

Hg + S HgS
Hg + _{Br2 HgBr2}

With many metals gives alloys (amalgams) (exothermic education). Couples and connections are extremely poisonous (collect in organism).
Mercury is not dissolved in the hydrochloric and diluted with chamois acids (among tension of metals mercury is after hydrogen; normal potential  ^{of Hg/Hg 2+} = +0,85 in). Mercury is easily dissolved in the concentrated nitric acid – mercuric nitrate (II) is formed:

Hg + _{4HNO3 Hg(NO3)2} + _2NO2 + _2H2O

At dissolution of mercury in the diluted nitric acid mercuric nitrate (I) is formed,

6Hg + _{8HNO33Hg2(NO3) 2} + 2NO + _4H2O

At dissolution of mercury in hot concentrated sulphuric acid depending on excess of mercury or acid salts of monovalent or bivalent mercury are formed:

Hg + _2H2SO4HgSO4 + _SO2 + _2H2O
2Hg + _{2H2SO4 Hg2SO4} + _SO2 + _2H2O

Mercury is dissolved in nitrohydrochloric acid:

3Hg + _2HNO3 + _6HCl3HgCl2 + _{2NO+ 4H2O}

HgO mercury oxide (II); red crystal or yellow amorphous powder; let's badly dissolve in water; solution has weakly alkaline reaction. <

Receiving 

	3000 C
2Hg + O2		2HgO
	4000 C

_{Hg2(NO3) 2 2HgO} + _{2NO2
2Hg(NO3) 2} 2HgO + _4NO2 + O2

Chemical properties.

It is easily recovered; when heating decays on mercury and oxygen. Reacts with acids with acids with formation of salts and waters.
HgS mercuric sulfide (II) (cinnabar) – bright red water-insoluble powder.

Hg + S HgS
^{Hg2 +} + ^S2-HgS

Halogenides.

Receiving 

Hg + _{Br2 HgBr2}
HgO + 2HCl (corrosive sublimate) _{of HgCl2} + H2O

Corrosive sublimate is also received dissolution of mercury in nitrohydrochloric acid.

 

Chemical properties:

_HgI2 + _{2KI K2[HgI4]} (Nessler's reagent)

Nessler's reagent is used as very sensitive analytical reagent for detection of ion _{of NH4+}:

Mercurous sulfate (II) and mercuric nitrate (II). Receive dissolution of mercury or mercury oxide (II) in the concentrated sulfuric or nitric acids respectively.

Hg + _2H2SO4 (hot, конц.) _HgSO4 + _SO2 + _2H2O
HgO + _{H2SO4 HgSO4} + _H2O
3Hg + _8HNO3 (конц.) _{3Hg(NO3) 2} + 2NO + _4H2O
HgO + _{2HNO3 Hg(NO3)2} + _H2O

More active metals easily force out mercury from its salts:

Cu + _{Hg(NO3) 2 Cu(NO3) 2 + Hg}

   

 

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