Inorganic Chemistry DepartmentGeneral and Inorganic Chemistry

In specialty 226 Pharmacy, industry pharmacy

Iryna VEDERNYKOVA,Doctor of Pharmaceutical Sciences, Professor

Elements of VIB-VIIB groups

1. Some properties of elements VIB group.2. Chromium. Chromium compounds. Chromium (III) cation and its

properties. Chromate and dichromate. Complex compounds of Chromium.

3. The Qualitative Reaction for Compounds Which Contain elements of VIB group.

4. Biological role compounds of elements VIB groupand their application in medicine.

5. Some properties of elements VIIB group.6. Manganese. Manganese compounds. Manganese (II) cation and its

properties. Permanganate ion.7. The Qualitative Reaction of Manganese (II) and permanganate ion.8. Biological role compounds of elements VIIB group

and their application in medicine.

Plan of Lecture

2

Actuality of theme

3

Biologically active substances of elements of VIB and VIIB groups are ofgreat importance in pharmacy and medicine.

Aim: Depending on the electronic structure of elements of VIB and VIIBgroups, their properties and the place they occupy in medicine and pharmacyare determined.

Specific goals:• Be able to write electronic formulas of elements of VIB and VIIB groups

in various degree of oxidation.• Know the ways to get and use them in medicine.

Theoretical questions for individual work

4

Tungsten and Molybdenum. Properties of simple substancesand their compounds.

Technetium and Rhenium. Properties of simple substancesand their compounds.

➢ General and inorganic chemistry: Textbook for students of higher schools Ye.Ya.Levitin, I.O.Vedernikova.– Kharkiv:Publishing House of NUPH :Golden Pages,2009. – 360 p.

➢ General and Inorganic Chemistry Laboratory Practicum / Ye.Ya. Levitin, I.O. Vedernikova, L.Yu. Klimenko, O.S. Kryskiv. – Kharkiv, 2020. – 106 p.

➢ General and inorganic chemistry: The lecture course for the students of pharmaceutical universities and pharmaceutical faculties of higher medical education / Ye.Ya. Levitin, I.O. Vedernikova, L.Yu. Klimenko, O.S. Kryskiv. – Kharkiv: NUPH Publishers, 2020. – 123 p.

➢ The collection of theoretical questions and tests in inorganic chemistry:for the students of higher school. / Ye.Ya.Levitin, I.O.Vedernikova.– Kharkiv: NUPH Publishers, 2007. – 76 p.

Bibliographical Guidance

5

The Elements of VIB Group

Chromium Cr24 [Ar] 4s13d

5

Molybdenum Mo42 [Kr] 5s

14d

5

Wolfram (Tungsten) W74 [Xe] 4f14

6s25d

4

1

• d- sublevels are completed with valence electrons, these elements are

the d-electronic families members

• these elements have 6 valence electrons, they are the elements

of VI-th group. The highest oxidation state is + 6

• chromium and molybdenum have only one electron on s-sublevel due

to symmetry rule (the power condition of an atom is considered more

slayable when the sublevel is filled completely or half )

Chromium

Chromium was discovered by Louis-Nicholas Vauquelin at 1797 in France.

Origin of name: from the Greek word "chroma"meaning "colour", named for the many coloured compounds known for chromium.

Brief description:

2

Chromium is a lustrous, brittle, hard metal. Its colour is silver-gray and it can be highly polished.

It does not tarnish in air, when heated it borns and forms the green chromic oxide. Chromium is unstable in oxygen, it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.

Occurence of chromium

Chromium is found as chromite

FeCr2O4 ore.

Siberian red lead - crocoite,

PrCrO4 is a chromium ore prized

as a red pigment for oil paints.

3

Molybdenum 2

Molybdenum is a silvery-white,

hard, transition metal. Molybdenum is

used in alloys, electrodes and

catalysts. The World War 2 German

artillery piece called "Big Bertha"

contains molybdenum as an essential

component of its steel.

Biological role:

molybdenum is a necessary element,

apparently for all species. Only very small

amounts are required. Molybdenum plays a role in nitrogen fixation, (a process

by which the normally unreactive nitrogen gas is turned into other compounds)

enzymes, and nitrate reduction enzymes.

Hazards and risks associated with molybdenum:

its compounds are encountered relatively rarely by most people. Unless known

otherwise, all molybdenum compounds should be regarded as highly toxic and

as teratogenic.

Tungsten 2

Pure tungsten is a steel-gray to tin-white

metal. Tungsten has the highest melting point

and lowest vapour pressure of all metals, and

at temperatures over 1650°C has the highest

tensile strength. It has excellent corrosion

resistance and is attacked only slightly by

most mineral acids.

Biological role:

tungsten has a limited biological role.

A number of enzymes (oxidoreductases) employ

tungsten in a way related to molybdenum,

(using tungsten.pterin complex).

The structure of a tungstoenzyme aldehyde ferredoxin oxidoreductase is known.

Hazards and risks associated with tungsten: tungsten metal does not normally

cause problems but all tungsten compounds should be regarded as highly toxic.

The metal dust presents a fire and explosion hazard.

Chromium compounds4

Conclusion:

0, +3, +6 are the most typical for chromium.

The o.s. increases the acidic properties increase

+2

0

+1

+3

+4

+5

+6

oxidation state

Cr simple compound, [Cr(CO)5] pentacarbonylchromium

CrO, CrCl2

Cr2O3, Cr(OH)3, Fe(CrO4)2 iron (II) metachromite

CrO3, K2CrO4

The preparation of compounds of chromium

(NH4)2Cr2O7 →

Cr + H2SO4 (dilute) →

Cr2O3 + N2 + 4H2O

Cr2O3

2Cr + 6H2SO4(conc.) = Cr2(SO4)3 + 3SO2 + 6H2O

Under the heating!

CrSO4 + H2

Chromium III oxide and hydroxide5

(NH4)2Cr2O7 → Cr2O3 + N2 + 4H2OThe reaction of de-combination of orange powder of ammonium

dichromate gives the green powder of chromium (III) oxide

Cr2(SO4)3 + 6NaOH → 2Cr(OH)3 + 3Na2SO4

2Cr3++3SO42- + 6Na++ 6OH- → 2Cr(OH)3 + 6Na+ + 3SO4

2-

Cr3+ + 3OH- → Cr(OH)3

The dark-green chromium (III) hydroxide precipitate is produced

Cr(OH)3 + 3NaOH → Na3[Cr(OH)6]

Cr(OH)3 + 3HCl + 3H2O → [Cr(H2O)6]Cl3

sodium hexahydroxochromate(III)

hexaaquachromium (III) chloride

Conclusion:

Chromium (III) oxide and hydroxide are amphoteric – react with acid and with base

The hydrolysis of chromium (III)

molecular equation: Cr2(SO4)3 + 3Na2S + 6H2O → 2Cr(OH)3(s) + 3H2S(g)

net ionic equation: 2Cr3+ + 3S2– + 6H2O → 2Cr(OH)3(s) + 3H2S(g)

6

Conclusion:

If salt is formed by the weak, insoluble basis and weak acid, unstable in a solution, the hydrolysis reaction proceeds up to the end (such salts do not exist in a solution and may be received only by thermal interaction of simple substances).

Irreversible hydrolysis (co-hydrolysis):

Conclusion:

Due to hydrolysis the solutions of chromium (III) salts have acidic medium

Indicator methyl-orange into these solution has pink color

The salts of chromium (III) undergoing hydrolysis. Under normal condition

they hydrolyse only at the thirst step

molecular equation: CrCl3 + H2O CrOHCl2 + HCl

net ionic equation: Cr3+ + H2O CrOH2+ + H+ pH<7

Aqua-complex Cr(III) has several hydrated-isomers:

[Cr(OH2)6]Cl3 is blue-violet color

[Cr(OH2)5Cl]Cl2 ·H2O is light-green

[Cr(OH2)4Cl2 ]Cl ·2H2O is dark-green

7Complex compounds of chromium (III)

The equilibrium between hydroxo- and aqua- complex Cr (III) can be

represented with a scheme:

OH_ H+

[Cr(OH2)6]3+ [Cr(OH)3(OH2)3] [Cr(OH)6]

3-

Conclusion:

Chromium (III) cation produces complex compounds with

coordination number c.n. = 6

Chromium VI oxide and hydroxide 8

K2Cr2O7 + H2SO4 → CrO3 + H2O + K2SO4

dark-red crystals

CrO3 + H2OH2CrO4 chromic acid

H2Cr2O7 dichromic acid

Electronic configuration of chromium in these compounds: Cr+6 [Ar] 3d04s0

Highest oxidation state, in the oxidation-reduction reaction – oxidazing agent:

CrO42- + 4H2O + 3ē → [Cr(OH)6]

3- + 2OH- E0 = - 1.216 V

Cr2O72- + 14H+ + 6ē → 2 Cr3+ + 7H2O E0 = 1.333 V

Conclusion:

Chromium IV oxide and hydroxides are acidic. Dichromate ion is a very strong oxidizing agent.

All the compounds of chromium IV are very toxic. They widely used like ox. agent in industry.

Potassium dichromate is used for qualitative identification of H2O2:

4H2O2 + K2 Cr2O7+ H2SO4 → 2CrO5 + K2SO4 + 5H2O

chromium (VI)

oxidediperoxides

O

O

O

OCr

O

Potassium chromate

K2CrO4 → 2K+ + CrO42-

Potassium dichromate

K2Cr2O7 → 2K+ + Cr2O72-

9Transformation chromate into dichromate

The salts of chromium in the solution can dissociate:

Conclusion:

The transformation of chromate ion into dichromate depends

on the value of pH

If pH<7 (acidic medium) the dichromate ion is stable

If pH>7 (basic or neutral medium the chromate ion is stable

molecular equation: 2K2CrO4 + H2SO4 K2Cr2O7 + K2SO4 + H2O

net ionic equation: 2CrO42- + 2H+ Cr2O7

2- + H2O

Equilibrium in the solution:

K2CrO4

K2Cr2O7

Oxidizing properties of dichromate ion

3NaNO2 + K2Cr2O7 + 4H2SO4 = 3NaNO3 + Cr2(SO4)3 + K2SO4 + 4H2O

+ 6ē + Cr2O72– + 14H+ 2Cr3+ + 7H2O 1 E0 = 1.33 V

– 2ē + HNO2 + H2O NO3– + 3H+ 3 E0 = 0.84 V

Cr2O72- + 14H+ + 3HNO3 + 3H2O = 2Cr3+ + 7H2O + 3NO3

- + 9H+

reducing agentoxidizing agent

5H+ 5H2O

E0cell = E0

ox. agent – E0red.agent = 1.33 – 0.94 = 0.39 V

if pH<7 chromium (III) is the product of reduction: Cr2O72- Cr3+

if pH ≥ then 7 the chromium (III) hydroxide is produced:

3(NH4)2S + K2Cr2O7 + H2O = 3S + 2Cr(OH)3 + 6NH3 + 2KOH

10

reducing agentoxidizing agent

Some compounds of chromium are insoluble

Two moles of Ag+ and one mole CrO42– ion appear in the saturated

solution for every of Ag2CrO4 dissolved.

2S S

Ag2CrO4 2Ag+ + CrO42–

The value of the solubility product constant of silver (I) chromate:

Ksp = 2.410-12

The expression of the solubility product constant of silver (I) chromate:

Ksp = [Ag+]2 [CrO42-] = (2S)2 S = 4S3

4S3 = 2.4 10-12 (molL-1); S = 8.43 10-5 (molL-1)

S(gL-1) = S(molL-1)M(Ag2CrO4) = 331.68.4310-5=2.7910-2(gL-1)

11

molar solubility

PbCrO4 lead (II) chromate Ksp = 2.810-13

Ag2CrO4 silver (I) chromate Ksp = 2.410-12

BaCrO4 barium chromate Ksp = 1.610-10

The reaction of qualitative identification

of chromium compounds

Cr2O72- + 2Ba2+ + H2O 2 BaCrO4 + 2H+

12

barium chromate

lead (II) chromate

Usage: insoluble

barium and lead

(II) chromate both

find use as

yellow pigments

The reactions for chromate ion :

CrO42-+ Pb2+ PbCrO4

The reaction for chromium (III) :

2Na3[Cr(OH)6] + 3H2O2 = 2Na2CrO4 + 2NaOH

– 3ē + [Cr(OH)6]3– + 2OH– CrO4

2- + 4H2O 2

+ 2ē + H2O2 2OH– 3

2 [Cr(OH)6]3– + 4OH– + 3 H2O2 = 2CrO4

2- + 8H2O + 6OH–2OH-

oxid. agentreducing agent

Yellow color appear

Chromium usage are:

• in alloys such as stainless steel, • in chrome plating and in metal ceramics, • in metallurgy to impart corrosion resistance and a shiny finish,• as dyes and paints,as a catalyst in dyeing and in the tanning of leather;

Chromium is an essential tracemineral required for normal protein,fat and carbohydrate metabolism.Chromium works, in part, byactivating the hormone insulin.

13

The Elements of VIIB Group

Rhenium

Technetium

Manganese

[Xe] 4f14

6s25d

5

[Kr] 5s24d

5

[Ar] 4s23d

5

Re75

Tc43

Mn25

1

• d- sublevels are completed with valence electrons, these elements are

the d-electronic families members

• these elements have 7 valence electrons, they are the elements

of VII-th group. The highest oxidation state is +7

Manganese• is a chemical element,

designated by the symbol Mn.

• It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals.

• As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

MnSO4

Manganese compounds 4

Conclusion: 0, +2, +4, +7 are the most typical for chromium.

The o.s. is increased the acidic properties is increased:

MnO is basic, MnO2 is amphoteric, Mn2O7 is acidic.

+2

0

+1

+3

+4

+5

+6

oxidation state

Mn simple compound, [Mn2(CO)10] decocarbonyldimanganese

MnO manganese (II) oxide, MnSO4

Mn2O3 manganese (III) oxide

Mn2O7, HMnO4 permanganic acid, KMnO4 potassium permanganate+7

K2MnO4 potassium manganate

MnO2 manganese (IV) oxide

Manganese II hydroxide5

Mn + 2HCl → MnCl2 + H2

MnCl2 + 2NaOH → Mn(OH)2 + 2NaCl

Mn2+ + 2Cl- + 2Na+ + 2OH- → Mn(OH)2 + 2Na+ + 2Cl-

Mn2+ + 2OH-→ Mn(OH)2

White manganese (II) hydroxide precipitate is produced

It can be produced in the

basic solution of Mn(II) salt:

MnCl2

The properties of manganese II hydroxide:

1) Mn(OH)2 + 2HCl → MnCl2 + 2H2O

2) Mn(OH)2 + NaOH

Conclusion:

Manganese (II) hydroxide has basic properties. It reacts with acid (1) and does

not react with base (2). This hydroxide can be reducing agent in the ORR (3).

3) Mn(OH)2 + O2 → MnO2 + H2O

2Mn(OH)2 + 4OH- + O2 + 2H2O 2MnO2 + 4H2O +4OH-

1O2 + 2H2O + 4ē 4OH-

2Mn(OH)2 + 2OH- - 2ē MnO2 + 2H2O4

2

Mn(OH)2 MnO2

The hydrolysis of manganese (II)6

Conclusion:

Due to hydrolysis the solutions of manganese (II) salts have acidic medium

Indicator methyl-orange into these solution has pink color

molecular equation: MnCl2 + H2O MnOHCl + HCl

net ionic equation: Mn2+ + H2O MnOH+ + H+ pH<7

The salts of manganese (II) undergoing hydrolysis. Under normal

condition they hydrolyse only at the thirst step

The reaction of dissociation:

MnCl2 → Mn2+ + 2Cl -

The reaction of hydrolysis:

Reducing properties of manganese (II)

E0 = 1.51V2– 5ē + Mn2+ + 4H2O MnO4¯ + 8H+

E0 = 1.449 V5+ 2ē + PbO2 + 4H+ Pb2+ + 2H2O

E0cell = E0

ox. agent – E0red.agent = 1.449 – 1.51 = – 0.061 V

7

reducing agentoxidizing agent

2MnSO4 + 5PbO2 + 6HNO3 = 2HMnO4 + 3Pb(NO3)2 + 2PbSO4 + 2H2O

4H+ 2H2O

5PbO2 + 20H+ + 2Mn2+ + 8H2O = 5Pb2+ + 10H2O + 2MnO4¯ + 16H+

Conclusion:

manganese (II) in the ORR is the reducing agent.

This is the reaction of qualitative identification of manganese (II) cation.

violet color appears

Potassium permanganate, KMnO4

is an important oxidizing agent.

For chemical analyses it is generally used in acidic solutions,

where it is reduced to colorless Mn2+:

E0 = 1.51 V

It is reduced to brown solid MnO2 in neutral solution:

E0 = 0.60 V.

It is reduced to green MnO42– manganate-ion in basic solution:

E0 = 0.56 V.

Potassium Permanganate: Structure and Formula

• Potassium permanganate is not as popular as other chemical compounds,

but we probably encounter it more often than we think.

• Potassium permanganate, also known as permanganate of potash or

Condy's crystals

The physical state of potassium permanganate

is an odorless solid,

and they look like dark purple or bronze colored

crystals.

If we dissolve these

crystals in water, the

solution becomes purple in

color.

Potassium permanganate

is able to oxidize many

substances, so it is very

well known as a strong

oxidizing agent, a

substance that accepts or

takes electrons from other

substances.

Potassium permanganate

is a chemical compound

consisting of two ions:

a potassium ion and a

permanganate ion.

Uses Of Potassium Permanganate

Potassium permanganate has various uses in various fields,

such as

➢ Purifying water.

➢ Creating an antiseptic solution.

➢ As an anti-fungal treatment for the hands and feet.

➢ As a cholera disinfectant

➢ Marking snow as an emergency signal.

➢ General disinfectant agent

Here Are Some Essential Uses Of

Potassium Permanganate.

1. Skin Infections :

Potassium Permanganate Treats Many Skin

Infections, Including Eczema, Dermatitis

And Acne.

2. Water Treatment :

Having A Strong Oxidizing Capacity, It Is

Ideal For Use In Water Treatment.

3. Fungal Infections :

Potassium Permanganate Foot Soaks

Treat Fungal Infections Such As

Athlete's Foot.

4. Fish Treatment :

Potassium Permanganate Can Be Used

To Treat Parasites On Individual Fish.

5. It Is Also Used As An Oxidizing Agent In Many

Chemical Reactions In Laboratories And Industry.

6. The Florists Use It For Making The Flowers

Look Fresh For A Longer Time.

7. Industrial And Chemical Uses :

It Is Used For Industrial Cleaning,

Bleaching, And Tanning.

Oxidizing properties of permanganate ion8

KMnO4 → K+

+ MnO4¯

Potassium permanganate dissociates in the water solution:

The electronic configuration of manganese

in the permanganate ion is: Mn+7 [Ar] 3d0 4s0

permanganate ion

MnO4¯ pH =7

Mn2+

MnO2

MnO4

2¯

in the acidic solution manganese (II) cation

is produced (MnSO4)

in the neutral solution the brawn precipitate of

manganese (IV) oxide is produced

in the basic solution manganate ion

is produced (K2MnO4)

Conclusion:

permanganate ion in the ORR is the oxidizing agent, the product of its reduction

depend on the type of solution

4521.01.2021

- 2ē10

5H2O2 + 2 MnO4- + 16 H+ = 5O2+ 10H+ + 2 Mn2+ + 8 H2O

O2

+ 5ē

H2O2

+ 4 H2O

5

2

H2O2 + KMnO4 + H2SO4 = O2 + MnSO4 + K2SO4 + H2O

+ 2H+

+ 8H+MnO4- Mn2+

6

5 2 3 5 2 8

Na2SO3 + KMnO4 + H2O = Na2SO4 + MnO2↓ + KOH+4 +7 +6 +4

MnO4- ↔

↔

MnO2

SO32- SO4

2- + H2O+ 2OH-

+ 2H2O + 4OH-

-2ē

+3ē

3

2

3SO32- + 6OH- + 2MnO4

- + 4H2O = 3SO42- + 3H2O + 2MnO2 + 8OH-

2

2 23 3 2

Na2SO3 + KMnO4 + KOH = Na2SO4 + K2MnO4↓ + H2O+4 +7 +6 +6

SO32- SO4

2- + H2O+ 2OH- ↔-2ē

MnO4- MnO4

2-↔+ē 2

1

SO32- + 2OH- + 2MnO4

- = SO42- + H2O + 2MnO4

2-

2 22

Reactions of potassium permanganate9

2KMnO4→ K2MnO4 + MnO2 + O2

The reaction of thermal decomposition is the method

of oxygen production in the laboratory:

Potassium manganate is not stable.

It is disproportionate:3K2MnO4 + 2H2O → 2KMnO4 + MnO2 + 4KOH

green color brown precipitate appears

+6 +7 +4

Manganese (VII) oxide is produced under the reaction

of potassium permanganate with acid:

2KMnO4 + H2SO4 → Mn2O7 + K2SO4 + H2O

The water solution of Mn2O7 is a very strong permanganic acid HMnO4,

the maximal concentration of this solution is 20%

Conclusion

• Manganese is used most commonly in steel

production to help improve strength, durability,

and toughness.

• It can be used in medicine to help support the

immune system, regulate your blood sugar, and

maintain bone regulation and reproduction.

• It is also used in gasoline to reduce engine

knock, and is used in alkaline batteries.

Thank you

for

attention!

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