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Metal are the class of chemical elements with certain characteristic properties. In everything usage, metals are elements and alloys such as iron, aluminium, copper, etc. which are lustrous, malleable solid usually good conductors of heat and electricity.
Till today more than 110 elements are known. To facilitate their study, these must be divided into certain classes. These have been mainly divided into metals and non - metals. One important factor, which distinguishes metals from non-metal in their electronic configuration. Metal have fewer electrons in their outermost energy level are lost rapidly and positive ions are obtained.
Na ( sodium )→ Na+(sodium ion ) + e-
Mg→ Mg2+ + 2e-
Al→ Al3+ + 3e-
sodium, potassium, calcium , magnesium , aluminium, copper, iron, silver, gold , zinc , platinum etc are some familiar examples of metals.
Hydrogen, carbon, nitrogen, oxygen, fluorine, phosphorous, sulphur, chlorine, bromine, iodine, etc are well known non-metals.
Metals are dividedinto two main groups.
The basic differences between metals and non-metals are listed below.
1.They exist as solid at ordinary temperature. [ exception: Mercury(liquid)]
1.They exist in all three states generally gases and solids. (Bromine is liquid)
2. They possess lusture when freshly cut.
2. They are nonlustureous. (exception- Iodine & graphite)
|3. They are electropositive.||3. They are electronegative.|
|4.They are generally good conductor of heat and electricity. (Exception - Pb )||4. They are poor conductor of heat and electricity. ( Exception - graphite )|
|5. They are malleable and ductile .||5. They are neither malleable nor ductile.|
|6. They can form alloys.||6. They cannot form alloys. ( exception - C , Si & P )|
|7. Metallic vapours are monatomic.||7. Non-metal are polyatomic molecule.|
|8. Oxides of metals are basic. ( Exception - Cr & Mn from acidic oxides and Al, Zn , Sn from amphoteric oxides)||8. Oxides of non-metals are acidic.( Exception - NO , H2O , CO and N2O are neutral oxides .|
|9. They are complexes in which the metals may form a part of cation or anion.|| |
9. They usually do not form complexes
|10. They behave as reducing agents because of their tendency to lose electrons.||10. They are generally behave as oxidizing agents since they have a tendency to gain electrons|
Elements which have intermediate properties between metals and nonmetals are called metalloids. Metalloids act as an electron donor with non-metals and as electron acceptor with metals. The elements like germanium, arsenic and antimony possess the character of both the metals and non-metals. Like non-metals, they show following properties .
Like metals , Arsenic possess metallic lustre, forms alloys and conducts electricity. Like copper, it also forms arsenious sulphide, As2S3 when H2 is passed through its salt solution. Antimony resembles arsenic in almost all respects.
An alloy is a homogenous mixture of two or more metals or metals with non-metals. As alloy possess metallic properties and it is prepared to get a product possessing desirable properties which the constituent elements do not posses. some examples of common alloys are :
Depending on the presence or absence of Fe as one component of alloys, they have been classified into two categories.
A homogeneous mixture of metals with mercury is called an amalgam. It is also defined as an alloy containing mercury as one of the constituents. eg. Sodium amalgam, Zinc amalgam etc. Most of the metals dissolve in liquid mercury to form the amalgam. But Fe, Co and Ni do not form the amalgam.
The metals occur in the earth's crust along with a number of rocky material and impurities. These are known minerals. Thus, the naturally occurring chemical substances in the earth's crust which are obtained by mining are known as minerals. Those minerals from which metal can be extracted economically are called ores, Thus, all ores are minerals, but all the minerals are not ores. Ores are usually associated with earthy materials called gangue or matrix.
Some important ores are listed below.
The country has yet to make the best use of these minerals for economic development. A table below records the occurrence of some common minerals in different parts of the country.
Table : Some Common Minerals in Nepal
|S.N.||Name of Meals||Name of Ore||Place where the minerals are found|
Jogimara (Dhading), Chobhar (Kathmandu), SurkhetOkhre ( Makawanpur) , Udaypur .
|3.||Cobalt||Cobalt ore||Palpa , Gulmi|
|4.||Copper||Copper ore||Chisapani gadhi, Galkot (Baglung), Udayapur, Dhading, Solukhumbu, Chobhar, Jugedi (Chitwan)|
|5.||Gold||Natural (traces)||Gandaki and Karnali rivers , Sunkoshi, Rapti river , Mustang , Swoyambhu (Halchowk area)|
|Phulchoki, Ramechap, Pyuthan, Bandipur, |
|7.||Lead/Zinc||Lead-zinc deposit||Ganesh Himal (Rasuwa), Galkot (Baglung), Phulchoki|
|Kharidhunga, Udayapur |
Ghosh, A.K. Chemical Calculations. 15th Edition. India: Scientific Book Company, 1991.
M.L Sharma & P.N. Chaudhary. Advanced Level Chemistry. 2nd Edition . Vol. I. Kathmandu, Nepal: Ekta Books, 2011.
Palak, K.R. Fundamentals of Chemistry. Kathmandu, Nepal: Ratna Pustak Bhandar, 2000.
Pathak, Prof. Dr. Tulsi Prasad. Rectified Chemistry. Kalikasthan, Kathmandu : Airawati Prakashan (P.) Ltd., 2014.