TRANSITION METAL

 

Week:   FOUR                                                    Date:                                                    

Period:                                  Duration: 1 HR 20 MIN.                                                  Average age of learners: 17YEARS

Subject:                                CHEMISTRY                                                                         Class: SS 3

Topic:                                    TRANSITION METAL

Sub topic: COPPER

Reference materials:

(1) ESSENTIAL CHEMISTRY, TONALD PUBLISHERS, I. O ODESINA

(2) NEW SCHOOL CHEMISTRY, AFRICAN FIRST PUBLISHERS, OSEI YAW ABABIO

(3) INTERNET

Instructional materials: copper wire.

Entry behavior: The students have been taught metals and their compounds.

Behavioural objective: At the end of the lesson the students should be able to:

1.       Define transition metal.

2.       List the members of the first transition series.

3.       State the physical properties of transition metal.

4.       Explain the extraction of copper.

CONTENT

TRANSITION METALS

The transition elements comprise those elements in the d-block of the periodic table in which the d-orbital are being filled.

THE FIRST TRANSITION SERIES

The atom of the metals in the first transition series have one or two 4s electrons like group I and II metal in the same period. In addition, they have partially filled 3d orbital which are responsible for their special properties of transition metal.

Element

Symbol

Atomic number

Electronic configuration

Scandium

Sc

21

[Ar] 3d14S2

Titanium

Ti

22

[Ar] 3d24S2

Vanadium

V

23

[Ar] 3d34S2

Chromium

Cr

24

[Ar] 3d54S1

Manganese

Mn

25

[Ar] 3d54S2

Iron

Fe

26

[Ar] 3d64S2

Cobalt

Co

27

[Ar] 3d74S2

Nickel

Ni

28

[Ar] 3d84S2

Copper

Cu

29

[Ar] 3d104S1

Zinc

Zn

30

[Ar] 3d104S2

PHYSICAL PROPERTIES OF TRANSITION ELEMENTS

1.       They are typically metal with high melting and boiling points.

2.       They have high densities with metallic luster.

3.       They are hard solid which are tough, ductile and malleable.

4.       They have small atomic volume.

5.       They have magnetic property i.e often paramagnetic rather than diamagnetic.

CHEMICAL PROPERTIES OF TRANSITION ELEMENT

1.       Forming compounds with variable oxidation states.

2.       A strong tendency to form complexes.

3.       Forming coloured compound

4.       Useful as catalysts.

COPPER [Cu]

Copper occurs mainly as the sulphide ore, copper pyrites CuFeS2 and Chalcocite ,Cu2S. Other sources are cuprite, Cu2O; malachite, Cu2S.CuS.FeS. Copper is a less reactive metal. It is very stable in air and can also be found in free metallic form.

EXTRACTION OF COPPER

Copper is extracted from its sulphide ore, CuFeS2. The ore is concentrated by froth floatation, in which air is blown into a large tank containing a mixture of the crushed ore and water to remove earthly impurities. The clean sulphide is then roasted in a limited supply of air to oxidized the iron and some of the sulphur to iron (ii) oxide and sulphur (iv) oxide respectively.

2CuFeS2(s) + O2(g)                        Cu2S(s) + 2FeO(s) + 3SO2(g)

SO2 escape from the top of the furnace. Silicon (iv) oxide [SiO2] is added and the mixture heated in the absence of air to remove the iron(ii)oxide in the form of iron(ii)trioxosilicate(iv) which floats on copper(i)sulphide as slag and is removed.    FeO(s) + SiO2(s)                 FeSiO3(l)

The copper(i)sulphide that remain is heated in a regular supply of air to produce copper with a purity of about 97.99%.       Cu2S(s) + O2(g)                          2Cu(s) + SO2(g)

Further purification is affected by electrolysis treatment of the impure copper. The cathodic copper formed is of high purity of about 99.9%.

PHYSICAL PROPERTIES OF COPPER

I.                    Cu is a reddish-brown, soft metal with a characteristic luster.

II.                  It is malleable and ductile

III.                It has relative high tensile strength

IV.                It is a good conductor of heat and electricity

V.                  It has a melting point of 1080oC and boiling point of 2300oC

VI.                The relative density is 8.95gcm-3

CHEMICAL PROPERTIES OF COPPER

1.       REACTION WITH AIR: Cu being low in the electrochemical series (e.c.s.) have weak electropositive property; hence it is very stable in pure dry air. However, when exposed to moist air for a long time, it become covered with a green coating of basic copper(ii)tetraoxosulphate (vi) {CuSO4.3Cu(OH)2} and trioxocarbonate(iv).

On heating in air Cu is readily oxidized to give black copper(ii)oxide.

2Cu(s) + O2(g)                 2CuO(s)

2.       REACTION WITH ACID: With hot conc. H2SO4, Cu is oxidize to copper(ii)tetraoxosulphate(vi) while the acid is reduce to sulphur(iv)oxide. Cu(s) + 2H2SO4aq                 CuSO4aq + 2H­2O(l)  + SO2(g).

With HNO3, the products depend on the concentration of the acid while nitrogen(ii)oxide is given off by dilute acid while nitrogen (iv) oxide is liberated by hot concentrated acid.

3Cu + 8HNO3                       3Cu(NO3)2 + 4H2O + 2NO

3Cu + 4HNO3                       3Cu(NO3)2 + 4H2O + 2NO2

3.       REACTION WITH SULPHUR: Cu at red heat reacts with sulphur vapour to form copper(i)sulphide.

Cu(s) + S(s)             Cu2S2(s)

4.       REACTION WITH HALOGEN: Cu at red heat is attacked by the halogens to form both copper(i) and copper(ii) halides. The proportion vary according to the amount of halogen. The less available the halogen the more copper(ii) halide is produced.

Cu + Cl2          CuCl(white)

Cu + Cl2          CuCl2(dark brown)

5.       DISPLACEMENT REACTION: Cu is displaced from its salts by most metal since it is very low in the e.c.s.

TEST FOR Cu2+

With NaOH – A few drops of aqueous NaOH to a solution of the unknown salt. The formation of a blue gelatinous precipitate which is insoluble in excess NaOH confirm the presence of Cu2+.

Cu2+ + 2NaOH             Cu(OH) + 2Na+

With aq. NH3 – Add few drops of aq. NH3 to the unknown salt solution. The formation of a blue ppt. of copper(ii) hydroxide which dissolve in excess aq. NH3 to give a deep-blue solution indicate the presence of Cu2+.

                Cu2+ + 2OH-              Cu(OH)2

                Cu(OH)2  + 4NH+4OH-                                  [Cu(NH3)4]2+deep-blue coloured ion   +  2OH-  + 4H2O

USES OF COPPER

I.                    It is used for making electrical wires and cable because it is very ductile.

II.                  Used in plumbing and roofing because it is attractive and resistance to corrosion

III.                Used in making alloy e.g. brass(Cu, Zn).

IV.                Serve as a catalyst in industry e.g. oxidation of methanol.

V.                  Copper is used in ornamental work as it is not attacked by air

PRESENTATION

I.                    The teacher explains transition metals

II.                  The teacher mentions the members of the first transition series.

III.                The students chorus the members of the first transition series.

IV.                The teacher explains the extraction of copper

V.                  The teacher explains the properties of copper

VI.                The students state some of the uses of copper

 

EVALUATION

 The teacher evaluates the lessons by asking the following questions:-

1.       Define transition metal.

2.       List the members of the first transition series.

3.       State the physical properties of transition metal.

4.       Explain the extraction of copper.

ASSIGNMENT

                Write the electronic configuration of each of the following ions of copper [29CU].

 I. CU+

 II CU2+

ii.     Give the number of unpaired electrons in each of the ions in (2ai) above.

I. CU

 II CU2+

iii.    Write the formula of one compound of cu+.

 

 

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