The Typical Characteristics Of Transition Metals Essay

, Research Paper

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(a) High Melting Point and Boiling Point The bonding between the atoms in transition metals is very strong. The strong

attractive force between the atoms is only weakened at high temperatures, hence

the high melting points and boiling points. For example: iron melts at

1535?C and boils at 2750?C BUT a Group 1 Alkali Metals such as sodium melts at

98?C and boils at 883?C. (b) High density Another consequence of the strong bonding between the atoms in transition

metals is they are tightly held together to give a high density. For example: iron has a density

of 7.9 g/cm3 and sodium has a density of 0.97 g/cm3 (and

floats on water while fizzing! water has a density of 1.0

g/cm3). (c) Form coloured compounds and ions in solution Transition metals tend to form more coloured compounds more than other

elements either in solid form or dissolved in a solvent. The colours of some

transition metal salts in aqueous solution are shown below. 1

2

3

4

5

6

7

8

9

10

Sc – scandium salts such as the chloride, ScCl3, are colourless

and not typical of transition metals

Ti – titanium(III) chloride, TiCl3, is purple

V – vanadium(III) chloride, VCl3, is green

Cr – chromium(III) sulphate, Cr2(SO4)3, is

dark green

Mn – potassium manganate(VII), KMnO4, is purple

Fe – iron(III) chloride, FeCl3, is yellow-orange-brown

Co – cobalt sulphate, CoSO4, is pinkish

Ni – nickel chloride, NiCl2, is green

Cu – copper(II) sulphate, CuSO4, is deep blue

Zn – zinc salts such as zinc sulphate, ZnSO4, are usually

colourless and not typical of transition metals (d) Catalytic Properties (1) The metallic elements themselves Many transition metals are used directly as catalysts in industrial chemical

processes and in the anti-pollution catalytic converters in car exhausts. For example iron is used in the Haber Synthesis of ammonia: Nitrogen + Hydrogen ? Ammonia or N2 + 3H2 ? 2NH3 via the Fe catalyst

atoms (2) The compounds of transition metals As well as the metals, the compounds of transition metals also acts as

catalysts. For example manganese dioxide (or manganese(IV) oxide), MnO2, a black powder,

readily decomposes an aqueous solution of hydrogen peroxide: Hydrogen peroxide ? water +

oxygen or 2H2O2 ? 2H2O + O2 via MnO2 as the catalyst