chemistry inorganic

7/25/2019 chemistry inorganic

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Giant molecule

structuresCHM 474



Overview……

Bonding Ionic Covalent Metallic

Structure Giant

ionic

Simple

molecular

Giant

covalent

Giant

Metallic

Example Sodium

chloride

Water Diamond Iron

Bonding an

d structure explains the properties ofa substance!



Macromolecule CrystalsA macromolecule is a big molecule that

contains a network of covalent bondsbinding its particles. he particles arenonmetal atoms. "xamples ofmacromolecules are graphite# diamond#silicon# silicon carbide# silica and boron

Substances withmacromolecular

structures are alwayssolids at room

conditions



Giant Covalent $tructures

GraphiteDiamond



Macromolecules……..• %ong chains of molecules

containing a very large number of

atoms

• "xamples& plastics# proteins# somecarbohydrates

• 'igher m.p.(b.p. than simplemolecules due to much strongervan der )aals* forces



general knowledge about

allotropes. Allotropes are di+erent forms of the same

element with their atoms arrangeddi+erently from one another. hey exhibit

di+erent behavior and characteristics. heconditions that changes allotropic formsare pressure# temperature and light. ,or

example# for carbon to turn into diamond#

we have to heat graphite to a very hightemperature under great pressure . -t is tosimulate the conditions /010 kilometers

down in the "arth*s mantle wherediamonds are formed.



A%%2324"$

Allotropy 5Gr. allos# other# and tropos#manner6

is a behaviour exhibited by certainchemical elements& these elements canexist in two or more di+erent forms#known as allotropes of that element. -n

each di+erent allotrope# the element7satoms are bonded together in adi+erent manner

http://en.wikipedia.org/wiki/Chemical_elements

http://en.wikipedia.org/wiki/Chemical_elements



Allotropes ofcarbon



8iamond

2ne of theallotropes of carbon

‘Allotropes’: Diferent (structural) orms o the

same element‘!sotopes’: Atoms o the same element "ith the

same num#er o protons #ut diferent num#er oneutrons

8iamond is one formof the element carbon.



8iamondHas a giant co$alent structure

Giant network o car#on atoms heldto%ether #& co$alent #onds in a

tetrahedral arran%ement

'hese our car#on atoms

orm a tetrahedron.



Diamond

"ach carbon is 9oined to fourother carbon atoms bystrong covalent bonds.

"ach carbon has fourcovalent bonds.



4roperties of 8iamond:ery high M.4. and B.4.

58iamond melts at about ;<00=C6'ardest natural substance

Reason&Carbon atoms are held together in a giant

rigid structure by strong covalent bonds.

A lot of energy is re>uired to break thesestrong covalent bonds.



4roperties of 8iamon

8oes not conductelectricityAll electrons are held

in the covalent bonds.

?o ions or freeelectrons to conductelectricity

-nsoluble in water



8-AM2?8

Carbon has an electronic arrangement of@#/. -n diamond# each carbon shareselectrons with four other carbon atoms forming four single bonds

-n the crystal of diamond#each carbon atom iscovalently bonded to fourother carbon atoms with

CCC bond angles of 01.<o

.he basic unit in diamond istetrahedron where eachcarbon can be made a

centre of a tetrahedron.



ses of 8iamond

sed in cuttin% other hardsolids (#ecause o its

hardness)*%* Diamond+tipped drills to

cut throu%h roc,



he physical properties of diam

. has a very high melting point 5almost /000=C6. :erystrong carboncarbon covalent bonds have to bebroken throughout the structure before meltingoccurs.

@. is very hard. his is again due to the need to breakvery strong covalent bonds operating in ;dimensions.

;. doesn7t conduct electricity. All the electrons areheld tightly between the atoms# and aren7t free tomove.

/. is insoluble in water and organic solvents. here areno possible attractions which could occur between



Graphite

Within the layer

"ach carbon atom is 9oined to threeother carbon atoms by strongcovalent bonds.

Arranged in rings of six atoms



$tructure of Graphite

Arrangementof carbon

atoms in one

layer

Arrangementof layers

Strong

covalent

bond

Strongcovalent

bond

Weak forcebetween

layers



G3A4'-"

Graphite is made up of parallel layers5sheets6 of carbon atoms arranged inhexagons

"ach carbon atom has a coordinationnumber of ; which means that it isbonded to three other carbon atoms. hegeometry is trigonal planar with the CCC

bond angles of @0o

Covalent

bonds

Van der Waals

forces



G3A4'-"Graphite has a

layer structure which is >uitedicult to drawconvincingly in

threedimensions. hediagram belowshows the

arrangement ofthe atoms ineach layer# andthe way thelayers are



he bonding in graphite

"ach carbon atom uses ; of its electrons to formsimple bonds to its ; close neighbours.

hat leaves a fourth electron in the bonding

level. hese spare electrons in each carbonatom become delocalised over the whole ofthe sheet of atoms in one layer.

he hexagonal layers of graphite are ;./ D apart

and held by weak attractive forces called the:an der )aals forces. hese weak forces areeasily broken# which explains the slippery orsoft nature of graphite. his enables graphiteto be used as solid lubricants as well as

pencils



'he ph&sical properties o %raphite

. has a high melting point# similar to thatof diamond. -n order to melt graphite# itisn7t enough to loosen one sheet fromanother. Eou have to break the covalentbonding throughout the whole structure.

@. has a soft# slippery feel# and is used inpencils and as a dry lubricant for thingslike locks. Eou can think of graphiterather like a pack of cards each card isstrong# but the cards will slide over eachother# or even fall o+ the pack altogether.)hen you use a pencil# sheets are rubbedo+ and stick to the paper.



he physical properties ofgraphite

;. has a lower density than diamond. his isbecause of the relatively large amount ofspace that is wasted between the sheets.

/. is insoluble in water and organic solvents for the same reason that diamond isinsoluble. Attractions between solventmolecules and carbon atoms will never bestrong enough to overcome the strongcovalent bonds in graphite.

<. conducts electricity. he delocalised electronsare free to move throughout the sheets. -f apiece of graphite is connected into a circuit#electrons can fall o+ one end of the sheet andbe replaced with new ones at the other end.



4roperties of Graphite

'he onl& non+metal thatconducts electricit&

Reason:

ach car#on atom hasone electron that is

not used in bonding.

,ree to move A#le toconduct electricit&



ses of Graphite4encil lead& Made of graphite

and claySince it is soft, it akes o andstick to paper when we write.

%ubricant 5for hot machines6

It does not decompose at hightemperatures.



4hysical 4roperties ofGiant Covalent$ubstances4hysical state

At room temperature# allsubstances with a giant covalent

structure are solids.$trong covalent bonds make it hard.

M.4. and B.4.'igh M.4. and B.4. because of its

strong covalent bonds



4hysical 4roperties ofGiant Covalent$ubstances$olubility in water

-nsoluble in water

"lectrical conductivity8o not conduct electricity 5except

graphite!6

Graphite

Diamond


http://slidepdf.com/reader/full/chemistry-inorganic 28/35Bonding Structure

1. What is the bonding structure of thecompound/element formed by :

a) Sodium toms

b) Chlorine and !otassium

c) Carbon and "#ygen

d) Carbon $in form of diamond)

Giant Metallic Structure

Giant Ionic Structure

Simple Molecular Structure

Giant Covalent Structure

(Metal Metal)-.

(Metal Non-metal)-.

(Non-metal Non-metal)-.

(Non-metal Non-metal)-.

Van der Waal’s Attraction between molecules



%elting point / Boiling point

&. %ap the compound/element to their

melting point ' boiling point.

/odium 0112 oC 3457 oC

6otassiumchloride

oC30oC

Car#on Dio8ide

+ 7 o

C 3 + 17 o

C

Diamond 772 oC 39452 oC

Stron bond ! Giant metallic structure

Stron bond ! Giant ionic structure

Wea" Van #er Waal’s Attraction

Stron bond ! Giant covalent structure



)hat are the types of attractive forces present in each of thefollowing substancesF $how how the physical properties arerelated to their structure and bonding.

5a6 8ry ice

5b6 $odium chloride

Answer



$a) (n dry ice the atoms are *oined together +ithin the molecules by

strong covalent bonds +hile only +ea, van der Waals- forces e#ist

bet+een molecules. he melting and boiling points of dry ice are lo+

since only +ea, van der Waals- forces are needed to be overcome

during the processes of melting and boiling. Besides dry iceconsists of simple molecules +ith no mobile electrons. hus it does

not conduct electricity. Carbon dio#ide is only slightly soluble in +ater

because it is nonpolar in nature.



$b) Strong ionic bonding e#ists bet+een oppositely charged ions

throughout the +hole lattice of a sodium chloride crystal. hus the

melting and boiling points of sodium chloride are very high.

%oreover sodium chloride is hard since the ions are closely pac,ed

and strong ionic bonds hold the ions together. (t is soluble in +ater

due to the solvation of ions $i.e. the attraction bet+een the ions and

+ater molecules +hich are polar) and is insoluble in nonpolar

solvents. Sodium chloride conducts electricity in the molten or

a0ueous state due to the presence of mobile ions in these states.

Bac



5b6 8escribe briey how the structures of the followingsubstances are related to their physical properties.

HuartI

Answer



uart2 is a substance +ith a giant covalent structure. (n the

0uart2 lattice each silicon atom is bonded tetrahedrally to four

neighbouring o#ygen atoms +hereas each o#ygen atom is

bonded to t+o neighbouring silicon atoms. his gives rise to a

tetrahedral diamondli,e structure. s the atoms are held

together by strong covalent bonds a large amount of energy is

re0uired to overcome the strong covalent bonds in the

processes of melting and boiling. hus 0uart2 has high melting

and boiling points. Besides 0uart2 is hard and rigid as the atoms

are fi#ed in their positions by strong covalent bonds. Since there

are no mobile electrons 0uart2 is a poor conductor of heat andelectricity. uart2 is insoluble in both polar and nonpolar

solvents



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