Assalamualaikum...Salam sejahtera kepada semua pembaca . saya mengalu-alukan kehadiran anda semua. Apa yang kamu boleh perolehi di sini? Ilmu pengetahuan? Maklumat? Semuanya ada..... Kita memerlukan saluran ilmu yang banyak untuk meningkatkan diri dalam segala ilmu pengetahuan yang ada di ruang lingkup muka bumi ini. Alam yang diciptakan oleh Allah s.w.t menceritakan seribu satu persoalan yang perlu dikaji, dinilai dan bermacam-macam lagi untuk kita ketahui semuanya sehinggalah apa yang ada dalam diri kita sendiri. Oleh itu, manfaatkan apa yang ada di dalam blog ini dan sumbangan idea anda amat dialu-alukan juga untuk kebaikan semua.
Posted by seorang insan
On
Friday, July 9, 2010
Transition Elements And Its Properties
- Transition metal is a block of metallic elements in between Groups 2 and 13 in the Periodic Table.
- They are much less reactive than the alkali metals.
- They do not react as quickly with water or oxygen as alkali metal.
Some General Physical Characteristics
- All transition elements are metals. Therefore they have the all the physical properties of metal such as:
- high melting point and boiling point
- hard,
- high density,
- high electrical conductivity,
- high tensile strength ,
- shinny surfaces,
- ductile
- malleable ,
High Melting Point and Boiling Point
- The bond between atoms of metal is called metallic bond and usually it is a very strong bond.
- Thus all the transition metals have high melting points and boiling points.
- For example: iron melts at 1535°C and boils at 2750°C.
- Mercury is a transition metal, but with unusual low melting point ( − 39oC).
Special Properties of Transition Elements
Form Coloured Compounds and Ions in Solute
- Transition elements tend toform coloured compounds either in solid form or dissolved in a solvent.
- Table below shows the colours of some aqueous solutions of ions of transition elements.
| Ion | Colour |
| Fe2+ | Light green |
| Fe3+ | Brown |
| Ni2+ | Green |
| Cr3+ | Green |
| Mn2+ | Pink |
| Cu2+ | Blue |
| Co2+ | Pink |
| MnO4- | Purple |
| CrO42- | Yellow |
| Cr2O72- | Orange |
Catalytic Properties
- Transition elements or their compounds have catalytic properties.
- A catalyst is a substance that speeds up a reaction but it itself does not change chemically after a reaction.
- Many transition metals are used directly as catalysts in industrial chemical processes.
- Table below shows the uses of transition elements or their compounds as catalysts in industries .
| Transition Elements or Its Compound | Uses |
| Platinum and rhodium | Used in the catalytic converters in car exhausts to reduce the emission of carbon monoxide and nitrogen |
| Platinum | Ostwald Process in the manufacture of nitric acid. |
| Nickel | Catalyst for 'hydrogenation' in the margarine industry.This process converts unsaturated vegetable oils into higher melting saturated fats. |
| Iron powder | Haber Process in the manufacture of ammonia. Iron catalyzes the reaction between nitrogen and hydrogen gas to produce ammonia. |
| Vanadium(V) oxide | Contact Process in the manufacture of sulphuric acid . In Contact Process, Vanadium(V) oxide catalyzes the oxidation of sulphur dioxide to sulphur trioxide. |
Variable Oxidation State
- A transition metal can have a variable oxidation state, which means it can form more than one ion.
- Table below shows the ions of transition elements that have
for example, iron(II), Fe2+ and iron(III) Fe3+; copper(I), Cu+ and copper (II) Cu2+.
Forming Complex Ions
- Transition elements can form complex ions.
- A complex ion is a polyatomic ions (positive or negative) consisting of a central metal ion with other groups bonded to it.
0 comments:
Post a Comment