p block(c fam) Flashcards
C fam
caarbon family
carbon
silicon
germinium
tin
lead
flerovium
elemental forms of carbon
graphite,diamond,coal
combined state of carbon
metal carbonates,hydrocarbons,CO2 in air
silicon present in nature as
silica and silicates
tin occur as
cassiterite
lead occur as
galena
who seen in tracce amout
germinium
valence shell Ec
ns2np2
increment of covalent radius
considerable increase from c to si ,si to pb small increase
reason for small increment in size from si to lead
due to presence of completely filled d and f orbitals in heavier atoms
IE
first IE is grreater than group 13.
generally decreases down the group
EN
more EN than grp 13.EN values from si to pb are almost same
physical propertiess
all are solids.
C and Si - non metals.
Ge - metalloid
Pb - soft metal
grp 14 elements have 4 electrons in outermost shell.common oxidation state?
+4 and +2
did carbon exhibits negative oxn state
yes
compounds in +4 oxn state generally covalent in nature .why
since the value of sum of first 3 IE are high
in heavier members the tendancy to shoe +2 state …
increases
most positive electron gain enthalpy (high)
Neon
all members when heated with oxygen forms oxides,in the form of
monoxide and dioxide
do they react with water
C,Si,Ge are unaffected by water.
Sn decompposes steam to form dioxide and dehydrogen.
Pb is unaffected
why pd is unafffected by water
it forms a protective oxide film
these elements can form halides of the formula
MX2 and MX4
do C react with halogen
no
sitric acid
Si(OH)4
anomolous behaviour of C
small in size,high EN,high IE,unavailability of d orbital
why covalency of C is limitted to 4 and others can expand their covalency
cos s and p orbitals of C is taking part in bonding..hence it can accomodate only 4 pair of electrons..others have d orbital and they can expand their covalency
catenation?
carbon have the tendancy to link with one another through covalent bonds to form chains and rings
how catenation possible in
C?
it has the ability to form ppi-ppi bond
small size
high EN
allotropes of Carbon
diamond,graphite,fullerene
order of IE
C>Si>Ge>Pb>Sn
hybridisation of diamond
sp3
enthalpy of formation of diamond
1.90KJ/mol
in diamond a carbon linked to four carbon in …….. faashion
tetrahedral
c-c bond length in diamond
154pm
in this structure ……….. covalent bonds are present
directional
hardest substance on the earth
diamond
it is used as an abrasive sharpening hard tools.which?
diamond
1 carat diamond
200mg
hybridisation of graphite
sp2
enthalpy of formation of graphite
0
in graphote layers are held by ……. force
van der waals force
distance btw 2 layers
340pm
each layer is composed of …………. rings of carbon atom
planar hexogonal rings
c-c bond length within in the layer
141.5pm
types of bonds btw carbon atom in hexagonal ring
3 sigma bonds btw 3 carbon atom.4th electrons forms pi bond
why graphites conduct electricity?
electrons are mobile over the whole sheet
graphite is used as a dry lubricant in machines running at high temperature,where oil cant be used .why?
graphites cleave easily btw the layers and therfore it is very soft and slippery
which is the most pure form of carbon.and its hybridisationn?
fullerene,sp2
how fulllerenes are prepared?
by heating graphite in an electric arc in the presence helium or argon..then condeses out C60 with C70 and other fullerenes
C60 named as
Buckminster fullerence
general name …….. refers to the family of spheroidal carbon cage molecules
fullerence
shape of C60
soccer ball
C60 contains
12 five membered ring
20 six membered rings
six membered rrings are fused to 5 membered rings and other 6 membered rings but 5 membered rings are only fused to 6 membered rings
both c-c single bond and double bond are present in this structure
yes
which are the impure amorphous forms of graphites or fullerenes
carbon black,coke,charcoal
……. is formed by burning hydrocarbon in limited air supply
carbon black
charcoal and coke are obtained by
heating wood and ccoal respectively in absence of air
why graphite is used for electrodes in batteries and industrial electrolysis.why?
graphite is a good conductor
…… made from graphite are inert to dil. acids and allkalies
crucibles
being highly porous,activated charcoal is used in
adsorbing poisonous gas