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Introduction
The different kinds of materials around us exist in variety of forms. Things like
aeroplanes, trains, building frames, automobiles or even different machines and tools, are
due to different properties of various metals. The non-metals exist as gases, liquids and
soft or hard solids. They occupy upper right positions in the Periodic Table. Carbon,
nitrogen, phosphorus, oxygen, sulphur, most of the halogens and the noble gases are non-
metals. They show a variety of chemical reactivities. They form different ionic and
covalent compounds, many of which are solids or gases.
8.1 METALS
Metals are the elements (except hydrogen) which are electropositive and form
cations by losing electrons. Metals can be categorized as detailed on the next page.
Scanned (auscanncr
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Sodium Atom 3s
electron configuration
having atoniie sire 186
Magnesium Atom
electron configuration
having atomic size
and
ionization energv 738
ionization eneruv
or nvagnesium is very high. It becotnes very dilTicult to retnove second electron froln the
Mg ion as nuclear charge attracts the remaining electrons strongly. As a result of this
attraction size of the ion decreases.
Similarly all the elen1ents of alkaline earth Inetals have high ionization energies
as cotupared to alkali tnetals as n in table 8. I l'able 8.1 Xtonlic Nunmber, Electronic
Configurations and ionization Energies
(k.J/nu)l) of Xlkali and ilkaline liarth 1Metals
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Metal
Atomic
Number
Electronic
Configuration
IE
Metal
Atomic
Number
Electronic
Configuration
IE2
3
[Hel 2
52()
4
I Hel 2 e
899
1757
Il
[Nel 3 s
l
Mg
12
[Nel 3 e
738
1450
19
419
20
[Arl 4 s
2
590
1145
37
[Kr•1 5 s
l
403
Sr
38
[Krl 5 e
549
1064
55
377
56
txel 6
503
965
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Introduction The different kinds of materials around us exist in variety of forms. Things like aeroplanes, trains, building frames, automobiles or even different machines and tools, are due to different properties of various metals. The non-metals exist as gases, liquids and soft or hard solids. They occupy upper right positions in the Periodic Table. Carbon, nitrogen, phosphorus, oxygen, sulphur, most of the halogens and the noble gases are nonmetals. They show a variety of chemical reactivities. They form different ionic and covalent compounds, many of which are solids or gases. 8.1 METALS Metals are the elements (except hydrogen) which are electropositive and form cations by losing electrons. Metals can be categorized as detailed on the next page. Scanned (auscanncr Inagncqitljn and aluminium. b. Moderately reactive : zinc, iron, tin and lead. c. Least reactive or noble : copper. Jnercury, silver and gold. comrnon tnetals and non-noctals in the periodic table arc si jown ill fipurc 8, Modern Periodic Tal)le Light metals Key: Colour of box of elements Metals Non-metals Metalloids Colour 019 Black Blue Red of elements Solid Liquid Gas Fi o . 8.1 Some common Inetals and non-tnetals. Important physical characteristics of metals are listed below: i, Almost all metals are solids (except mercury) lie They have high mélting and boiling points. (except alkali metals) iii. They possess metallic luster and can be polished. They are malleable (can be hammered into sheets), ductile (can be drawn into wires) and give off a tone when hit. They are good conductor of heat and electricity. They have high densities. vii. They are hard (except sodium and potassium) Important chemical properties of metals are: They easily lose electrons and form positive ions. ii, They readilv react with oxygen to form basic oxides. They usually form ionic compounds with non-metals. They have metallic bonding. Scanned witfb Causcanncr 8.101 Electropositive Character Metals have the tendency to lose their valance electrons. This property ()t• metal is termed as electropositivity or metallic character. The more easily a metal loses its electrons, the Inore electropositive it is. The nun)ber of electrons lost by an of a nnetal is called its valency. For example. soditltn atoni can lose I electron to forni a positive 1011 So the valency ol' sodiull) Illetal is l. Similarly zing metal can lose 2 electrons from its valence shell. Therefore, its valeney is 2. zn(s) Trends of electropositivity Electropositive character increases down the group because size ot atoms increases. For exajnple. lithium Jnetal is less electropositive than sodilll'l which is in Electropositive character decreases across the period from left to right in the periodic table because atomic sizes decrease due to increase of nuclear charge. It means elements at the start of a period are more Inetallic. This character decreases a s we move from left to right along the period. Electropositivity and ionization energy Electropositive character depends upon the ionization energy which in turn depends upon size and nuclear charge of the atom. Small sized atoms with high nuclear charge have high ionization energy value. In this way atoms having high ionization energy are less electropositive or metallic. That is the reason alkali metals have the largest size and the lowest ionization energv in their respective periods. Therefore, they have the highest metallic character. For example, a comparison Of sodium and magnesium metals is given below for understanding. Scanned witfb Causcanncr Sodium Atom 3s electron configuration having atoniie sire 186 Magnesium Atom electron configuration having atomic size and ionization energv 738 ionization eneruv or nvagnesium is very high. It becotnes very dilTicult to retnove second electron froln the Mg ion as nuclear charge attracts the remaining electrons strongly. As a result of this attraction size of the ion decreases. Similarly all the elen1ents of alkaline earth Inetals have high ionization energies as cotupared to alkali tnetals as n in table 8. I l'able 8.1 Xtonlic Nunmber, Electronic Configurations and ionization Energies (k.J/nu)l) of Xlkali and ilkaline liarth 1Metals Metal Atomic Electronic Number Configuration IE Metal 52() [Hel 2 3 [Nel 3 s l Mg Il 419 19 [Kr•1 5 s l 403 37 Sr 377 55 Atomic Number 4 12 20 38 56 Electronic Configuration I Hel 2 e [Nel 3 e [Arl 4 s2 [Krl 5 e txel 6 IE2 899 1757 738 1450 590 1145 549 1064 503 965 Scanned innsca.nncr Name: Description: ...
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