كيمياء لغات Transition elements للصف الثالث الثانوى 2016

The first Series of Transition elements

Economic Importance of Elements of the

first Transition series

:(1- Scandium (₂₁Sc

.It is not abundant in the earth’s crust and it has limited uses

:(2- Titanium (₂₂Ti

It is silver-grey metal and more abundant in the earth’s crust it is the second element in the first transition elements after iron & characterized by

.a- very hard.                             b- Resists corrosion

.(c- Has low density but more than Al (1,5 times

.d- Keep its strength at high temperature

“G.R: “First session 96

.Titanium is better used than Aluminum in the manufacture of rockets and supersonic planes

.Because it keeps its strength at high temperature

:(3- Vanadium (₂₃V

It is silver- grey metal and its compounds have several beautiful colours and characterized by its hardness and corrosion resistance. So, its alloy with iron (ferrovanadium alloy) is used in the manufacture of car springs

:Its compounds

Vanadium pentaoxide (v₂o₅), which is used as a catalyst in sulphuric acid industry (contact method) and in themanufacture of benzoic acid.

:(4- Chromium (₂₄Cr

.It is silver-grey, its name is derived from the Greek word Chromos, and characterized by

.a- very active.                                              b- its ions are coloured

.c- Resists the oxidation by oxygen at room temperature

“G.R: “First session 91-92

. Chromium metal resists the Action of atmospheric effects although it is chemically active -

Due to the formation of an oxide layer on the surface, where the oxide molecules are larger than the atoms of the lement and forms “non-porous layer which prevents further reaction with atmospheric oxygen”. [passivity

.NB:Iron compound are covered with chromium and not the chromium compounds are covered with iron

.Chromium is used in electroplating metals -

.To resist corrosion and make them more attractive

:Uses of chromium

.a-   In stainless steel and surgical tools (Fe-Cr-Ni) which contains 12% Cr

b-   In Nickel alloys, e.g.: nichrome, which contains 15% Cr, which is used in heating coils and in electric irons and electric furnaces

:(Manganese (₂₅Mn

Manganese is the third most abundant transition metal, it resembles iron in appearance and it is used in steel production

.G.R: Manganese is used in the manufacture of steel

.Because it reacts with oxygen during the production and prevents the formation of bubbles in steel during cooling

:Compounds of manganese

.Manganese dioxide (MnO₂) is used as a catalyst and as an oxidizing agent in dry cells -

.Potassium permanganate (KMnO₄) is used as antiseptic and as an oxidizing agent -

:(6- Iron (₂₆Fe

It is the most abundant transition metal in the earth's crust. And used in the manufacture of cars, ships, and tools and it will be discussed later

:(Cobalt (₂₇Co

.Cobalt compounds have been used in colouring glass -

.It occurs in vitamin B₁₂. Cobalt has a biological importance, comment -

.It is used in formation of several alloys -

.NB: Cobalt has 12 isotopes

:Cobalt compounds

.Hydrated Cobalt chloride which is used in the manufacture of secret ink -

.Anhydrous cobalt chloride which is used in weather prediction -

:.G.R

.Hydrated cobalt (II) chloride (CoCl₂) is used in the manufacture of secret ink -

Because hydrated cobalt (II) chloride has a pale pink colour in diluted colution and changes to a dark blue colour on dehydration

.Anhydrous cobalt (II) chloride is used in atmospheric predictions -

.Because anhydrous cobalt (II) chloride has dark blue colour and changes to pale pink on hydration

:(Nickel (₂₈Ni

.It is used in manufacture of about 3000 alloys, such as nichrome alloy -

.It is used as a catalyst in hydrogenation of oils -

.It is used in plating metals to protect them from corrosion -

It is used in the manufacture of vessels which are used to store liquid HF, caustic soda (NaOH). Because nickel can -

.resist their attack

.It is ductile -

:.G.R

.Caustic soda (NaoH), acids as; liquid HF, are Kept in nickel vessels -

.Because nickel resists Corrosion and resists their attack

.Nickel is used to plate other metals -

.To protect them from oxidation and corrosion

:(Copper (₂₉Cu)

.it is a soft reddish metal of high thermal and electric conductivities -

.the free element is used in electric eqiupments and wires -

.it is used in alloys as Brass (Cu + Zn), bronze, and coins -

.G.R:Copper is used in electric wires

.Because copper is a good conductor of electricity

:(Question: Choose from column (B) the suitable materials in column (A

The Electronic Configurations and oxidation states of the 1^st Transition series

NB: Elements of the first transition series lies in the fourth period after ₂₀Ca. The 5 orbitals of the sublevel 3d are successively filled with unpaired electrons till Mn, then pairing takes place

:From the table

The oxidation numbers increase in the first transition series from Sc to a maximum in Mn then decrease again to Zn with exception for the elements of group I-B Because from Sc to Mn the number of unpaired electrons increases and Mn to Zn pairing of electrons takes place.(Give Reason)

NB: It is clear that the maximum oxidation number of any element can not exceed its group number, the only deviation is noticed for group I-B elements (Cu, Ag, Au

On oxidation (i.e. when the atom losses electrons) the atom loses first electrons of 4S (having high quantum number), Followed by the electrons of 3d (lower quantum number) to give the different oxidation states

Transition elements are characterized by having many oxidation states. Due to the sublevel 3d is not completely filled and the sublevels (3d and 4S) are nearly equal in energy, so, when the atom gains a gradual amount of energy, the two electrons of the sublevel 4S lost firstly, then the electrons of the sublevel 3d in sequence, as the difference in ionization energies is small

:The atom or the ion becomes stable when the sublevel d is

a- Empty (d⁰) as in case of Sc⁺³ and Ti⁺⁴

b- Half filled (d⁵) as in case of Mn⁺² and Fe⁺³

c- Completely filled (d¹⁰) as in case of Zn⁺²

(Question: Iron (II) is easily oxidized to Iron (III), while Manganese (II) is not easily oxidized to Manganese (III

:Because

Chromium (₂₄Cr) and Copper (₂₉Cl) have abnormal electronic configuration. Because in Cr₂₄ one electron will transfer from 4S to 3d, so, the sublevels become half filled and this makes the atom more stable and in Cu₂₉ one electron will transfer from 4S to 3d, so, the sublevel 4S becomes half filled and 3d sublevel becomes filled and makes the atom more stable

Scandium gives (+3) oxidation state not (+2). Because the difference between the 2^nd and 3^rd ionization potential is small, so scandium loses two electrons from 4S sublevel then one electron from 3d sublevel to be more stable, i.e.; the stability of Argon.                           (Give reason

The ionization potential increases with the increase of oxidation number

:G.R

.it is difficult to obtain Sc⁺⁴ ion by normal chemical methods -

Because the difference between the third I.P and fourth I.P is very large due breaking of a complete energy level

.Potassium has only one oxidation state while vanadium has more than one oxidation state -

Because in K, the increase in the I.P. is very large breaking a complete energy level, but vanadium has more than one oxidation state because the two sublevels 4S and 3d have nearly equal energies, so, they lost  their electrons in sequence when the atom is oxidation

₁₉K: ₁₈[Ar], 4S¹                                 ₂₃V: ₁₈[Ar], 4S² , 3d³

“Transition Elements: “very important

They are the elements in which the sublevels d or f are occupied by electrons, but not completely filled either in the atomic state or in any of its oxidation state

:Questions

Can the coinage metals which are ₂₉Cu (4S¹ , 3d¹⁰), ₄₇Ag (5S¹ , 4d¹⁰), and ₇₉Ag (6S¹ , 5d¹⁰) be considered as -

?transition elements

?Can the metals ₃₀Zn (4S² , 3d¹⁰) , ₄₈Cd (5S² , 4d¹⁰), ₈₀Hg (6S² , 5d¹⁰) be considered as transition elements -

.G.R: The main transition elements in the three series are 27 and not 30 elements

                                                                   (write answer)

General properties of the first transition elements

.G.R:The transition elements are metals

Firstly

:The transition elements have the following physical properties

.They are malleable and ductile -

.They have metallic luster -

.They are good conductors of heat and electricity -

.(They have high (melting point and boiling point -

.They form alloys with non transition elements accordingly they are metals -

.Their atomic sizes are small -

:Secondly

Transition elements have less than 4 electrons in their outer most shell (the fourth energy level contains one or two electrons (4S¹ or 4S²), accordingly they are metals

:Thirdly

Transition elements lose their valence electrons during the chemical reaction giving positive ions, form basic oxides, replace hydrogen in diluted acids, accordingly they are metals