p block(B fam) Flashcards
does He belongs to p block?
no (s block)
oxdtn state (max oxn state)
grp no - 10
max oxn state
ns electrons + np electrons
oxides of non metals
acidic
oxides of metals
basic
highly reactive non metals + highly reactive metals
ionic compounds
highly reactive non metals + highly reactive non metals
covalent compounds
max covalency of first members is limited to 4 due to
abscence of d orbital
first member has a unique tendency to form Ppi-Ppi bonds with itself and others due to
small size
absence of d orbital
heavier elements forms _____ bonds instead of ppi-ppi bonds
dpi-ppi.
dpi-dpi.
heavier among alkali grp
Fr
heavier among chalcogens
Po
heavier among noble gases
Rn (rad.act.noble)
heavier among alkaline earth metals
Ra (rad.act.alk.ear.met)
a hard black coloured non metal
boron
aluminium and others are
soft metals
why boron is hardest
it exist as B12 units
icosahedral sturcture
20 trrigonal face
12 cornes
isotopes of boron
B10 (19%)
B11(81%)
Boron exist in crystalline and amorphous forms.then their reactivities..
crystalline - inert due to strong structure.
amorphous - little reactive.
boron does not react with whom.
cold water,hot water,non oxidising acids(HCl,aq.alkali)
boron react with whom to give
molten alkali to form borates
3rd most abundant element and most abundant in the eraths crust
aluminium
order of abundance of boron family in earths crust
Al>Ga>B>In=Tl
boron occur as
boric acid - H3PO3.
borax - Na2B4O7.10H2O
kernite - Na2B4O7.4H2O
colemnite -Ca2B6O11.5H2O
aluminum occur as
gibbsite- Al2O3.3H2O.
bauxite- Al2O3.2H2O.
diaspore-Al2O3.H2O.
corundum of alumina-Al2O3.
nature of corundum
hard and abrasive
all the trivalent compounds of grp 13 like BF3,AlCl3 are?
elecctron deficient(electron pair acceptor,lewis acid)-
if shielding effect in atom is highe then its size become
high
high shielding effect affects..
low ionisation energy,electronegativity,nuclear charge
order of shielding power?
s>p>d>f
Ga,In,Tl shows slight difference in properties when compares with boron and aluminium due to
due to weak shielding effect of d electrons
size of galium is lower than aluminium due to
weak shielding effect of d electrons present in galium
order of covalent radius
B<Ga<Al<In<TL
inert pair effect
inertness of valence s electrons to take part in chemical bonding
along a group inert pair effect..
increases
boron has has stable +3 effect due to
weak inert pair effect
thalium has stable +1 state due to
strong inert pair effect
order of stability in +3 state
B>Al>Ga>In>Tl
order of stability in +1 state
B<Al<Ga<In<Tl
moving down a group lower oxn state become
more stable
Tl3+ act as OA but Tl+1 do not act a RA
coz down the grp lower oxn state is more stable
who can show +1 state among boron family
Ga,In,Tl
Ga and In are more stable ine +3 than +1.true or false?
true
Halides of Ga and In ______ in solution
disproportionate(3GaX—>GaX3+2Ga)
TlX will not disproportionate due to
stable +1state
thalium show some similarity in properties with alkali metals
due to +1 state
thalium is called duckbill platipus why?
coz it shows the properties of other elements
boron only forms covalent compounds but aluminium and other forms
both ionic and covalent compounds
does an.Alcl3 forms covalent bond?
yes and it is non conducting
an.alcl3 exist as
chlorobridged dimer
structure of an.alcl3
monomer-sp2-trigonal planar
dimer-sp3-tetrahedral(inside angle=118 degree,inside bond length=206pm)(bondangle with another alcl3=79
and bondlength 221pm)
wht abt hydrated alcl3
ionic and conducting(alcl3.6h2o)
why boron halides do not forms dimer
boron is small it cant hold large sized halogen atoms
why boron do not forms ionic compounds
bcoz the high values of first three ionsation enthalpies
why alf3 is insoluble in an.HF and soluble in KF?
an.HF is highly covalent and hydogen bonded.hence it will not produce F^(-).but KF is highly ionic and easily release F^(-).
why boron easily forms complexes than aluminium
due to small size and high electronegativity
BF3 precipitates out AlF3 from soluble complexes ( like..)
Na3[Alf6]
aluminium utensils should not be kept in water overnight.why?
aluminium reacts with water and dissolved oxygen to give a thin layer of al2o3 on surface.
2Al + O2 +H2O –> Al2O3 + H2
little Al2O3 dissolves in water to form Al3+ wchich is injurius to health
atomic radii of grp 13 elements is smaller than the corresponding group 2.why
due to increase of nuclear charge
Ga has lower radius than aluminiumm
yah
IE order
B>Tl>Ga>Al>In
why thalium has a higher ionisation enthalpy than in indium?
in case of thalium increased nuclear charge by 32 units overweighs the shielding effect of HF and 5d electrons
electronegativity decreases from boron to aluminium and then increases due to
weak shielding efffect of d anf f electrons
EN values
B - 2.0
Al - 1.5
Ga -1.6
In - 1.7
Tl - 1.8
boiling point decreases from boron to thalium due to
increase of size and hence decrease of interatomic interactions
how melting point affects
decrease from boron to galium and then increases
very low melting point for galium (30 deg).?
Ga 2 molecules are held by weak van der waals force
neighbourhood of galium(solid) [existance of Ga2]
one cclose neighbour at a distance of 243pm and 6 more neighbours at 270-279pm
why liq galium on solidification, volume increases upto 3%
in solid galium molecules are held by weak forces
which are the 2 liq metals having melting point 30 deg
Ga,Cs
density increases from boron to thalium
increase of mass overweighs the increase pf size
when heated wirth air grp 13 elemts forms
trioxide or sesqui oxide(M2O3)
oxide of boron is acidic.wht abt others
oxide of Al and Ga are amphoteric.
oxide of In and Tl are basic
when boron and akuminium heated with aair forms
a mixture of both oxides and nitrides (b2O3,Al2O3)
boron does not react with water or steam but
red hot boron reacr with cold water and forms oxide
2B+3H2O–>B2O3+3H2O
aluminium react with cold water but ………. prevent further reaction
oxide layer
gallium and indium will not reacct with water.Thalium react with….
moist air
4Tl+2H2O+O2–>4TlOH
certain metals when dipped in c.HNO3 becomes incaative due to formation of protective oxide layer.those passive metals are
Fe,Cr,Al,Ni,co
c.HNO3 can store in Al containers.why?
aluminium become passive with hno3
boron doesnt react with non oxidising acids .wht abt others?
Al and others react with oxidsing and non oxidising acids by liberating hydrogen
boron react with alkali (abv 773K) molten.wht abt others
being amphoteric galium and aluminiumreact with.aq. alkali by evolving H
reactn with halogen
gives trihalide(except TlI3)
halides of boron
BF3 - colourless gas
BCl3 - colourless liq
BBr3 - colourless liq
BI3 -white solid
backbond has a …… chracter bcoz it results after the formation of sigma bond
pi bond
boron halides are weak lewis acid.why?
electron deficiency of boron is compensated by ppi-ppi back bond
BF3 is the weakest lewis acid
coz fluorine form strongest back bond due to small size high electron density
order of acidic strength among trihalides
BF3<BCl3<BBr3<BI3
stronger the backbond.weaker will be the lewis acid char.as size of boron fam increase lewis acid char decreases.
BCl3>AlCl3>GaCl3
observed bond length of B-F in BF3
130pm (much less than sum of cov radii of B and F)
bond order of BF3
tot.no.of bonds/ta.resonance=4/3=1.33
during hydrolosis boron halides fumes in air due to
formation of hydrohalic acid (HCl)by hydrolisis
BF3 will note fume in air.why?
it only undergo partial hydrolysis and form mixture of fluroboric acid (HBF4) and will not form HF.
BF3 (lewis acid) combines with NH3 (lewis base) to give
1:1 addition prdt adducct
hybridisation of BF3 and NH3 and its product
BF3–>sp2 hybridisation–>tirgonal planar
NH3—>sp3—>trigonal pyramid
product–>sp3 and tetrahedral
anomalous behaviours of boron
1.boron is a non metal
2.boron exhibit allotropy but others not
3.boron has very high melting and boiling points than other
4.boron only forms covalent compounds
5.oxides and hydroxides of boron are acidic,but those of aluminium and galium-amphoteric,indium and thallium-basic.
6.hydrides of boron are highly stable but those of others are less stable.
7.boron reacts with active metals to give borides but others will not. Mg3B2
diagonal relationship between boorn and silica
1.both are non metals
2.both cannot form higher form higher oxdn states and Si4+
3.both exist in amorphous and crystalline forms
4.both forms acidic oxides
5.both forms weak acid(boric acid,silicic acid)
6.both forms hydrides-boranes,slianes(B2H6,SiH4
