physical properties of group iiib elements

8/3/2019 Physical Properties of Group IIIB Elements

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Physical Properties of Group IIIB Elements

Group III B includes boron, aluminum, gallium, indium and thallium. All the members of group IIIB containthree electrons in the outermost orbit. Hence, they have an outer electronic configuration of ns2np1. As the outermost electrons are present in the p-shell they are included in the P-block. Here is a list of physical properties bythese elements.

Physical properties:Atomic and ionic radius: atomic radius increases from boron to thallium. From boron to aluminum, the

atomic radius increases greatly. This increase is due to greater screening effect caused by the eight electronspresent in the penultimate shell. This is not seen in case of boron as it has only two electrons in the penultimateshell. In case of ionic radius, it increases from boron to thallium.

Density:Density increases from B to TI. This is due to increase in the size of the atom. Of all the elements,

aluminum is of very low density and is widely used as a structural material.

Melting and boiling points:Melting point decreases from B to Ga and then it gradually increases. Boron has a very high melting point

due to its existence as a giant covalent polymer in both solid and liquid states. Gallium has a very low meltingpoint and remains as liquid up to 2000.

Ionization energy:Though the members of p-block have large nuclear charge and small size, the first ionization energies of

these elements are less than the corresponding values of s-block elements. The electrons are far away from thenucleus and are held less tightly. Hence, they can be removed very easily. However, the average of the first threeionization energies is very high and decrease as we move down the group.

Electropositive character:Electropositive nature increases from B to TI. Boron acts as a semi-metal while all the other elements

show metallic nature.

Oxidation states:As there are three electrons in the outermost orbit, they show oxidation states of +1 and +3. Boron

exhibits only the +3 oxidation state and all the other elements show both the oxidation states. The stability of +1oxidation state increases as we move down the group. Thus, thallium which shows a +1 oxidation state is highlystable. This is due to the inert pair effect. (Inert pair effect means the two s-electrons in the outer shell remainpaired and do not participate in compound formation).

Ability to form ionic compounds:The tendency to form ionic compounds increases as we move down the group. Boron forms only covalent

compounds. This is mainly due to its high ionization energy and small size. The small size of boron enables it toexert strong polarizing effect on neighboring atoms and pulls off the electrons from neighboring atoms. As theionic size increases as we move down the group, the tendency to form covalent bond decreases.Oxidation potential or reducing property: the oxidation potentials of the elements of group III B are very high.This is due to high heat of hydration which is due to high charge and small radius of trivalent ions M 3+. Aluminumis a very strong reducing agent.Complex formation: the smaller size and greater charge of group IIIB elements enable them to have a greatertendency to form complexes than the s-block elements.

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Physical constants of group 13 elementsBack to Top

1. Atomic and ionic radiiBack to Top

The atomic and ionic radii of group 13 elements are compared to corresponding elements of group 2. This isdue to the increase in nuclear charge when one moves from, element of group 2 to group 13 in the sameperiod. As the elements are considered from left to right in the period, the magnitude of nuclear chargeincreases but the electrons are added to, the same shell. Since the electrons in the same shell do notscreen each other, therefore, the electrons experience greater nuclear charge. In other words, effectivenuclear charge increases and thus, size decreases. Therefore, the elements of this group have smaller size

than the corresponding elements of second group. On moving down the group both atomic and ionic radiiare expected to increase due to the addition of new shells. However, the observed atomic radius of Al (143pm) is slightly more than that of Ga (l35 pm).

Explanation:

While going from Al (Z =13) to Ga (Z =31) there are also ten elements of the First transition series of d-blockfrom (Z = 21 to 30) which have electrons in the inner d-orbitals. The d-orbitals do not screen the nucleuseffectively because of their shapes and poor penetration power. As a result, the effective nuclear charge inGa becomes more than in Al and its atomic radius, therefore, decreases slightly.

2. Melting and boiling pointsBack to Top

The melting points and boiling points decrease on moving down the group. However, the decrease inmelting points is not as regular as in boiling points.

3. Ionization energiesBack to Top
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The first ionization energies of group 13 elements are less than the corresponding members of the alkalineearths.

Explanation:

The first electron in the case of group 13 elements (ns2np1) is to be removed from p-orbital while in case ofelements of group 2; the electron has to be removed from s-orbital. Since p-orbitals are at slightly higherenergy than the s-orbitals, the electron in the atoms of group13 elements is weakly held by the nucleus and,therefore, the first ionization energy is less. However, second (IE2) and third (IE3) ionization energies arequite high. When one electron is removed from outermost p sub-shell, the resulting ion has completely filleds-orbital (ns2). Therefore, it becomes difficult to remove the second electron.

On moving down a group, the ionization energies in general, decrease.

Explanation:

This is due to increase in atomic size and screening effect, which is more than to compensate the effect ofincrease in nuclear charge. Consequently, the electron becomes less and less tightly held by the nucleus aswe move down the group. Hence, ionization energy decreases down the group.

The study of the above table shows an anomalous behavior - ionization energy decreases sharply from B toAl and then the ionization energy of Ga is unexpectedly higher than that of Al.

Explanation:

The sharp decrease in I.E. from B to Al is due to increase in size. In case of Ga, there are ten d-electrons inits inner electronic configuration. Since the d-electron shield the nuclear charge less effectively than the s-and p-electrons, the outer electron is held fairly strongly by the nucleus. As a result, the ionization energyincreases slightly in spite of the increase in atomic size as one moves from Al to Ga. The similar increase is

also observed from In to Tl, which is due to the presence of 14 f-electrons in the inner electronicconfiguration of Tl, which have very poor shielding effect.

Electropositive (or metallic) characterBack to Top

Due to high ionization energies, the elements of group 13 are less electropositive as compared to elementsof group 2. On moving down the group the electropositive (metallic) character increases because ionizationenergy decreases. For e.g., Boron is a non-metal white the other elements are typical metals.
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Oxidation statesBack to Top

The atoms of these elements have three valence electrons, two in s-subshell and one in the p-subshell (ns2

np1). Therefore, all these elements can show maximum of +3 oxidation state. The common oxidation states,observed for group 13 elements are +3 and + l as shown below. The stability of the + 1 oxidation stateincreases in the sequence Al < Ga < In < Tl.

Except boron and aluminium, the other elements also show +1 oxidation state. The +1 oxidation statebecomes more stable as one moves down the group from boron to thallium. In case of last element,thallium, +1oxidation state has been found to be more stable than + 3 oxidation state.

Explanation:

This is explained on the basis of inert pair effect. The elements of group 13 have three electrons in theirvalence shell (ns2npl) and, therefore, exhibit, oxidation state of + 3. However, it bas been observed that inaddition to + 3 oxidation state, they also exhibit oxidation state of +1. The +1 oxidation state becomes moreand more stable as one goes down the group from B, Al, Ga, In to Tl. The +1 oxidation state of Tl is morestable than +3 oxidation state. For e.g., thallous compounds such as TlOH and TlClO4 are more stable thantheir thallic compounds. This is attributed to the inert pair effect. In the case of last element, after theremoval of one electron from p-orbital, the remaining ns2 (e.g. 6s2) electrons behave like stable noble gasand do not take part formation. This reluctance of the s-electron pair to take part in chemical combination iscalled inert pair effect. This helps to explain the stability of lower oxidation states for the heavier elements ofa group.

Some physical constants of Group 14 elementsBack to Top

C Si Ge Sn Pb

Atomic radius (pm) 77 118 122 140 146

Ionic radius (pm) - 40 53 69 78

M4+M2+

- - 73 118 119

Ionisation energy IE1(k.J mol-1) 1086 756 761 708 715

IE2 2352 1577 1537 1411 1450

IE3 4620 3228 3300 2942 3081

IE4 6220 4354 4409 3929 4082

Electro negativity 2.5 1.8 1.8 1.8 1.9

Melting point (K) 4373 1693 1218 505 600

Boiling point (K) - 3550 3123 2896 2024

The variation of the physical properties among the members of the group is discussed below:
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DensityBack to Top

The density of the members belonging to this group is found to increase down the group as usual.

Explanation:

It is because of the increase in mass per unit volume.

Atomic radiiBack to Top

The atomic radii of group 14 elements are smaller than the corresponding elements of group 13.

Explanation:

This is because as one moves from group 13 to group 14 elements within the same period, the nuclearcharge increases and consequently the size decreases. Within the group, the atomic radii increase on goingdown the group due to increase in the number of energy shells.

Ionization energyBack to Top

As the sizes of elements belonging to group 14 are smaller than the corresponding elements of group 13,their first ionization energies are higher than those of corresponding members of group 13. Among themembers of the same group, the ionization energies (IE) follow the order C > Si > Ge > Sn < Pb.

Explanation:

In general, the ionization energy decreases down the group due to increase in size and screening effect ofinner electrons. Therefore electrons become less and less tightly held by the nucleus and ionization energydecreases. The electropositive character (or metallic) increases down the group due to decrease inionization energy.

Metallic characterBack to Top

The elements of group 14 are less metallic due to relatively large values of ionization energies as comparedto elements of group 13. The metallic character however increases down the group from C to Pb.
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ElectronegativityBack to Top

The elements belonging to this group are more electronegative than elements of group 13. It is becausethese have a small size. The electronegativity value decreases from top to bottom in the group.

CatenationBack to Top

A remarkable property of carbon is its ability to form compounds in which carbon atoms are linked to oneanother in chains or rings. This property of forming chains of identical atoms is called catenation. Theproperty of catenation depends upon the strength of atom-atom bond. The greater the strength of the atom-atom bond, greater is the extent of catenation. The elements of group 14 exhibit catenation. It is mostextensive in the case of carbon because C-C bond is very strong. On going down the group, the atom-atombond strength decreases and hence the extent of catenation also decreases. It varies in the order: C > > Si

> Ge Sn > > Pb

AllotropyBack to Top

A characteristic property of the elements of groups 14 is that these show allotropy.

Allotropy is the existence of an element in two or more forms, which are significantly different in physicalproperties but have similar chemical properties. The difference may be due to difference in crystal structure,the number of atoms in the molecule of a gas or the molecular structure of a liquid.
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For e.g, Carbon has two important allotropic forms i.e., diamond and graphite. In diamond, carbon is sp3

hybridized and has a network of tetra-coordinated carbon atoms. Thus it is a network solid.

On the other hand, in graphite the carbon atom is sp2 hybridized. Thus, it has a layer structure i.e., the threecovalent bonds form hexagonal layers. The fourth unhybridized p-electron of each carbon forms anextended delocalized p-bonding system due to pp-pp bonds forming tendency of carbon atoms. Variouslayers are held together by weak Van der Waal forces. It is for this reason that it is used as a lubricant. For

e.g, suspension of graphite in oil is used as lubricant in heavy machinery. It is known as oil dag. Similarly,colloidal dispersion of graphite in water is called aqua dag.

Oxidation StatesBack to Top

Oxidation States of Group 14 elementsBack to Top

The electronic configuration of the valence shell reveals the presence of four valence electrons. Now, inorder to acquire the noble gas configuration the carbon family members have to gain or lose four electronsforming ions of the type M4+or M4-. Since the formation of such ions would require a large amount of energy,which shall not be available under the conditions of bond formation, therefore they neither lose nor gain fourelectrons but share electrons to get stable noble gas configuration. Hence, the elements of group 14 formcovalent bonds in their compounds, with the highest oxidation state of + 4.

The elements of this group also exhibit an oxidation state of + 2. It is observed that the lower oxidation statebecomes more stable with increase in atomic number, down the group. This is due to the inert pair effect.The elements in their lower oxidation state of + 2 are expected to form ionic bonds whereas in the higher

oxidation state of + 4 these can form only covalent bonds in their compounds. This indirectly means that aswe move down the group, the tendency to form ionic compounds increases. The stability of the divalentstate increases markedly in the sequence. Ge< Sn

Some important physical constants of group 15elementsBack to Top

N P As Pb Bi

Atomic radius (pm) 70 110 120 140 150

Ionic radius (pm) 171 (N3 - ) 212 (P3 - ) 222 (As3 - ) 76 (Sb3 + )

Ionisation energy IE1(k.J mo1-1) 1402 1012 947 834 703

IE2 2856 1903 1798 1594 1610

IE3 4577 2910 2736 2443 2446

Electronegativity 30 2.1 2.0 1.9 1.9
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N P As Pb Bi

Melting point (K) 63 317.1 1089 904 544.4

Boiling point (K) 77 553.5 888 1860 1837

Density (g cm- 3) 0.879 0.879 5.778 6.697 9.808

The important physical characteristics are discussed below:

Atomic and ionic radiiBack to Top

The atomic and ionic radii of group 15 elements are smaller than the atomic radii of the corresponding group14 elements. This is because of increased nuclear charge. On going down the group, the atomic radiiincrease due to the increase in number of shells.

Melting and boiling pointsBack to Top

Melting points (except for antimony and bismuth) and boiling points increase on going down the group fromN to Bi.

Ionization energiesBack to Top

The first ionization energies of the group 15 elements are higher than the corresponding members of thegroup 14 elements.

Explanation:

The larger ionization energy is due to greater nuclear charge, small size and stable configuration of theatoms of group 15 elements. The electronic configuration of atoms of group 15 is half filled,

energies. On going down the group, the ionization energies decrease. This is due to increase in atomic size andscreening effect, which overweigh the effect of increased nuclear charge.

ElectronegativityBack to Top

The electronegativity values of elements (of group 15 are higher than the corresponding elements of group14.

Explanation:
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The elements of group 15 have smaller size and greater nuclear charge of atoms and therefore they havehigher electronegativity values. On going down the group the electronegativity value decreases. This is dueto increase in size of the atoms and shielding effect of inner electron shells on going down the group.

Metallic characterBack to Top

The elements of group 15 are less metallic. However on going down the group, the metallic characterincreases from N to Bi. For e.g.,, N and P are non-metallic, As and Sb are partly non-metallic while Bi is ametal.

CatenationBack to Top

The elements of group 15 also show a tendency to form bonds with itself known as catenation. All theseelements show this property but to a much smaller extent than carbon. For e.g., hydrazine (H2N-NH2) has

two N atoms bonded together, hydrazoic acid, (N3H), has three N-atoms, azide ion, , has also three Natoms bonded together, while diphosphine (P2H4) has two phosphorus atoms bonded together. The lessertendency of elements of group 15 to show catenation in comparison to carbon is their low (M-M) bonddissociation energies.

Bond C - C N - N P - P As - As

Bond energy 353.3 163.8 201.6 147.4

AllotropyBack to Top

Except nitrogen and bismuth, all other elements of this group show allotropy.

For e.g.,

Phosphorus exists as - white, black or red phosphorus

Arsenic exists as - yellow or grey arsenic

Antimony exists as - yellow or silvery grey

allotropic forms.

Oxidation statesBack to Top
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These elements have five electrons in the valence shell. The loss of five electrons is quite difficult becauseof energy considerations. Hence they do not form ionic compounds by loss of 5 electrons. On the otherhand, these elements can also gain three electrons to complete their octets. But gain of 3 electrons is alsonot energetically favorable. However, they do form N3-and P3- ions by gaining three electrons from highlyelectropositive elements, e.g. Mg3N2, Ca3P2.

In addition to - 3 oxidation state, the elements of group 15 exhibit +3 and +5 oxidation states. For e.g.,

phosphorus forms pentahalides such as PF5, PCl5 (+5 oxidation state) and trihalides PCl3, PF3 (+3 oxidationstate).

Nitrogen exhibits various oxidation states from -3 to +5 in its hydrides, oxides and oxo acids.

For e.g.,

Compound Oxidation state

NH3 Ammonia - 3

N2H4 Hydrozine - 2

N2 Nitrogen 0

N2O Nitrous Oxide + 1

NO Nitric Oxide + 2

N2O3 Nitrogen trioxide + 3

N2O4 Nitrogen tetraoxide + 4

N2O5 + 5

Some physical properties of the elements of group 16

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Group 16 Elements (Chalcogens) - Introduction

1. Atomic and ionic radii

Property Oxygen Sulphur Selenium Tellurium Polonium

Atomic radius (Ao) 0.73 1.09 1.16 1.35 -

Ionic (M2+) radius (Ao) 1.40 1.85 1.98 2.21 -

Ionization energy (kJ mol-1) 1314 1000 941 869 -

Electronegativity 3.5 2.5 2.4 2.1 2.0

Electron affinity (k.J mol-1) 141.4 208.8 195.5 190.0 -

Melting point (K) 54 392 490 723 527

Boiling Point (K) 90 718 958 1263 1235

Oxidation state - 2 - 2, + 2 + 4, + 6 - 2, + 2 + 4,+6 - 2, + 2 + 4,+6 - 2, + 4

Density (g cm-3) (in solid state) 1.14 2.07 4.79 6.25 9.4


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Back to Top

The atomic and ionic radii of the elements of this group increase on going down the group. This is due to theincrease in the number of electron shells.


The ionization energies of the elements of oxygen family are less than those of nitrogen family. As we movedown the group from oxygen to polonium, the ionization energy decreases.

Explanation:

We expect that the ionization energy of oxygen should be more than that of N because of decrease in size.However, oxygen has unexpectedly low ionization energy than N. This is due to the reason that nitrogen hascompletely half filled orbitals and the configuration is stable because half filled and completely filledconfigurations have extra stability. But the configuration of O is less stable and therefore, has less ionizationenergy.

As one moves down a group there is increase in nuclear charge. But at the same time the atomic size aswell as the number of inner electrons, which shield the valence electrons from the nucleus increase. The

overall effect of increase in atomic size and the shielding effect is much more than effect of increase innuclear charge. Consequently, the outermost electron is less and less tightly held by the nucleus as wemove down the group and hence ionization energy decreases.


The melting and boiling points increase with the increase in atomic number as we go down the group.

Explanation:

When we move down the group, the molecular size increases. As a result, the magnitude of the van der

Waals forces also increases with increase in atomic number and therefore melting point also increases. Themelting point of polonium is, however, small.

4. ElectronegativityBack to Top

Oxygen is the second most electronegative element, the first being fluorine. The electronegativity decreaseson going down the group. This is due to increase in size of the atoms.
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5. Metallic and non-metallic characterBack to Top

The first four elements namely oxygen, sulphur, selenium and tellurium are non-metals. The non-metalliccharacter is stronger in O and S and weaker in Se and Te. On the other hand, last element is markedlymetallic. However, it is radioactive and is only short-lived. .

6. Electron affinityBack to Top

The elements of this family have high electron affinities. The values decrease down the group from sulphurto polonium. Oxygen unexpectedly has low electron affinity. This is attributed to the small size of oxygenatom so that its electron cloud is distributed over a small region of space and therefore, it repels theincoming electron. Thus, the electron affinity of oxygen is unexpectedly less in the family.

7. CatenationBack to Top

Catenation is the tendency of an atom to form bonds with identical atoms. In this group only sulphur has astrong tendency for catenation. Oxygen also shows this tendency to a limited extent. Thus the polyoxidesand polysulphides of the following types are known:

H2O2, H - O - O - H

Polyoxides

H2S2, H-S-S-H

H2S3, H-S-S-S-H

H2S, H-S-S-S-S-H

Polysulphides

8. Elemental stateBack to Top

Oxygen exists as diatomic molecule. Under normal conditions oxygen exists as a gas. In oxygen moleculethere is pp-pp overlap between two oxygen atoms forming double bond, O = O. The intermolecular forces inoxygen are weak van der Waals forces and therefore, oxygen exists as a gas. On the other hand the otherelements of family do not form stable pp-pp bonds and do not exist as M2 molecules. On the other hand theother atoms are linked by single bonds and form polyatomic complex molecules. For e.g., sulphur andselenium molecules have eight atoms per molecule (S8 and Se8) and have puckered ring structure. Thepuckered ring structure of S is as shown below.
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The Puckered ring structure of S8 molecule

9. AllotropyBack to Top

All the elements of the group exhibit allotropy. For e.g., oxygen exists as O 2 and O3 (ozone). Sulphur existsin a number of allotropic forms such as rhombic, monoclinic, plastic sulphur. All these allotropic forms ofsulphur are non-metallic. Selenium has two common forms-red and grey. Similarly tellurium and poloniumoccur in allotropic forms.

Some physical properties or group 17 elementsBack to Top

ElementAtomic

Radius (A)

Ionic

Radius (A)

Ionization Energy

(kJ mol-1)

Melting

point (K)

Boiling

point (K)

Electron

affinity

Electro

negativity

F 0.72 1.86 1681 53 85 332.6 4.0

Cl 0.99 1.81 1255 172 238 348.5 3.0

Br 1.14 1.95 1142 266 332 324.7 2.8

I 1.33 2.16 1007 386 456 295.5 2.5
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1. Atomic and ionic radiiBack to Top

The halogens have the smallest atomic radii in their respective periods due to maximum effective nuclearcharge. Among themselves, the atomic and ionic radii increase with increase in atomic number. This is dueto increase in the number of electron shells.


The ionization energies of halogens are very high. This indicates that they have very little tendency to loseelectrons. However, on going down the group from fluorine to astatine, the ionization energy decreases. Thisis due to gradual increase in atomic size, which is maximum for iodine. Consequently, it has the leastionization energy in family.


The melting and boiling points of halogens increase with increase in atomic number down the group.

Explanation:

The forces existing between these molecules are weak Van der Waals forces, which increase down thegroup. This is also clear from the change of state from fluorine to iodine. At room temperature, fluorine andchlorine are gases; bromine is a liquid while iodine and astatine are solids.

4. Electron affinitiesBack to Top

(i) All these have maximum electron affinities in their respective periods. This is due to the fact that theatoms of these elements have only one electron less than the stable noble gas (ns2np6) configurations.Therefore, may have maximum tendency to accept an additional electron.

(ii) In general, electron affinity decreases from top to bottom in a group. This is due to the fact that the effectof increase in atomic size is much more than the effect of increase in nuclear charge and thus, the additionalelectron feels less attraction by the large atom. Consequently, electron affinity decreases. .

(iii) Fluorine has unexpectedly less electron affinity than chlorine. Therefore, chlorine has the highest

electron affinity in this group. The lower electron affinity of fluorine as compared to chlorine is due to verysmall size of the fluorine atom. As a result, there are strong inter-electronic repulsions in the relatively small2p subshell of fluorine and thus the incoming electron does not feel much attraction. Therefore, its electronaffinity is small. Thus, electron affinity among halogens varies as: F < Cl > Br > I.

Chlorine has the highest electron affinity in the periodic table.

5. ElectronegativityBack to Top
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Halogens have large electronegativity values. The values decrease down the group from fluorine to iodinebecause the atomic size increases and the effective nuclear charge decreases. Fluorine is the mostelectronegative element in the periodic table.

6. Metallic or non-metallic characterBack to Top

Because of very high ionization energy values, all halogens are non-metallic in character. The non-metalliccharacter decreases as we go down the group. Therefore, the last element, iodine is a solid with a metalliclustre and forms positive ions such as I+ and I3+.

7. ColorBack to Top

All the halogens are colored. The color of different halogens are given below:

Explanation:

The color of halogens is due to the fact that their molecules absorb radiations from visible light and the outerelectrons are easily excited to higher energy levels. The amount of energy required for excitation dependsupon the size of the atom. Fluorine atom is the smallest and the force of attraction between the nucleus andthe outer electrons is very large. As a result, it requires large excitation energy and absorbs violet 1ight (highenergy) and therefore, appears pale yellow. On the other hand, iodine needs very less excitation energy andabsorbs yellow light of low energy. Thus it appears dark violet. Similarly, we can explain the greenish yellowcolor of chlorine and reddish brown color of iodine.

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physical..carbon silicon

colour of

element

colourless (diamond), black

(graphite)gray

germanium tin lead

colour ofelement

white metallicwhite metallic (beta), gray(alpha)

bluish whitemetallic

Applications and Uses

The group 14 elements each have very different and a wide range ofapplications within industries, varying from the coating of tin cans to thehigh-tech silicon chip.

Halogen Fluorine Chlorine Bromine Iodine

Colour Light yellow Greenish yellow Reddish brown Dark violet
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Carbon

The first element in this group has a large number of uses, namely dueto the different chemical and physical properties of its 3 allotropes,Graphite, Diamond and the Fullerenes.

Diamond: diamond has an exremely high commercial value as agemstone and there is a lot of importance placed on it. It is also well-known for being the hardest and strongest known substance/mineral,this feature has made its extensive use in industry extremely important.It is applied in the cutting and grinding of tools , abrasives and otherhard materials.

Graphite: graphite has numerous properties as a result of its structurethat allow it to be used in various applications and industries.At hightemperatures this element is used as a lubricant to prevent friction,

wear, overheating and rusting (due to the layers of carbon rings whichmake up its lattice). The material is also added to lead used in pencils asthe layers are able to slide over each other and onto the paper sincethey are bonded by the weak van der Waals forces. These weak bondsbetween adjacent layers are also the reason for graphite being a goodelectrical conductor. The electrons involved in these bonds aredelocalised over the rings of carbon and are free to move throughoutthe structure, parallel to the layers. It is this property, therefore, that isimportant for the use of graphite electrodes in electrolysis processes forextraction.

Charcoal: charcoal and animal charcoal are microcrystalline forms ofgraphite which are supported on calcium phosphate. Their adsorptionproperties are commercially important for gases and for purifying andclarifying liquids. This property is a result of charcoal being a porousform of carbon. Charcoal from wood is also used for burning.

Carbon fibres have great tensile strength as they contain graphitecrystallites, and so these are used for strengthening materials includingplastics.

Many composites of carbon are reinforced with fibres making them

chemically inert , thermally stable, high strength, rigid and highlyresistant to thermal shock. For these reasons, certain compounds areused for the outer body of the space shuttle.

The extensive range of hydrocarbons that carbon forms have intenseimportance in the petrochemical industry.
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Silicon andGermanium

These 2 elements in group 14 hold major importance in the semi-conductor industry and electronics. Their semi-conduction propertieshave revolutionised the computer industries with the production of the

silicon chip. Silicon is of great value in these industrial areas, whilegermanium is being taken over by more advanced and efficientmaterials being developed.

The various different compounds that these elements form have manydifferent properties and uses within numerous areas.

Silica is an extremely important commercial material for glassproduction and in the form of sand for the building industry. Silica gel isused as a drying agent, as the stationery phase in chromotography, andas a heterogeneous catalyst.

Germanium oxide has very important optical properties and hasspecialised use in lenses, infra-red detectors, and in spectrometers.

Tin

Tin also has a number of uses within everyday industries. As a result ofits high resistance to corrosion it has been used as the plating on steelcans for many years and is unlikely to be replaced as it is not a toxicmetal.

The metal itself is soft, but when added to other materials to produce tinalloys often the properties are much improved. These alloys includepewter, solder metal, bronze and ddie casting and have a greatercommercial value than pure tin.

Tin dioxide is an opacifier and used in enamels and paints, also in gassensors. Tin based compounds and chemicals act as flame retardants.

Lead

Lead is also a soft metal in its pure form and is used in the plumbingindustry, as old water pipes, due to being malleable. Its use is declining,however, as awareness of its toxicity increases. Lead has been acommon componant in the mixtures for petrol fuels over many years.This is also diminishing as a result of its toxicity, as its use as an additiveto form tetraethyl in leaded fuels can attack the nervous system andcause great damage. More environmentally friendly lead-free fuels,therefore, are taking over the leaded counterparts.
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Large amounts of lead are used in another area of the automobileindustry, as lead-acid batteries. It is also used for building roofs since itresists corrosion and is malleable. It is a dense metal and acts as aneffective shield foe preventing unecessary exposure to X-rays and othertypes of radiation.

Lead salts are extremely toxic and accidental ingestion of such salts willresult in acute poisoning. Lead based paints are also common, yet longterm exposure can cause chromic poisoning.

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s=69262595911755&id=40419321637991

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Group&ModuleId=2&keepThis=true&TB_i...

Uses: Carbon forms numerous and varied compounds with limitless applications. Manythousands of carbon compounds are integral to life processes. Diamond is prized as a gemstoneand is used for cutting, drilling, and as bearings. Graphite is used as a crucible for meltingmetals, in pencils, for rust protection, for lubrication, and as a moderator for slowing neutronsfor atomic fission. Amorphous carbon is used for removing tastes and odors.

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wiki.answers.com/Q/What_are_some_interesting_facts_about_carbon
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physical properties of group iiib elements

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