Intro to P block and group 13 Flashcards
List all of the Group 13 elements
Boron, Aluminium, Gallium, Indium, Thalium
Which group 13 elements are metals?
aluminium, gallium, indium, thalium, boron is a metalloid
Describe the trends in ionisation potential of the group 13 elements
Boron is the highest, high Zeff. Then they go down with two anomalies, Gallium is slightly higher than Al and In because it has an electron in the 4p electron which has a larger Zeff that in the 3p orbital for Al. And Thalium has a higher IP than Indium because Zeff is larger for the 6p electron than the 5p electron
Give an example of an application for each element in group 13
Boron - borosilicate is pyrex glass, also borax is noisy putty
Aluminium - Packaging, alloys for aircraft/bikes
Gallium - High temp. thermometers
Indium - transparent conducting oxides
Which of the halides of boron (BF3,BCl3 and BBr3) is the strongest Lewis acid and why?
The strongest Lewis acid is BBr3 because there is poor overlap of the full p orbitals on Br and the empty p orbital on boron, therefore no electron density is donated to the boron. BF3 is the weakest Lewis acid because electron density is donated from the p orbitals on the F to the empty P orbital on the boron, therefore boron is less electron deficient and its Lewis acidity is reduced.
Draw the reaction of BX3 (lewis acid) with NMe3
BX3 + NMe3 —> adduct
Draw the mechanism of the hydrolysis of BX3 to form boric acid
H2O attacks B —> B(OH)3
Which halide of boron will be hydrolysed the fastest?
BBr3 because it is the most acidic and the hydrolysis relies on the acidity of the halide
Why must BX3 be held under anhydrous conditions when used as a catalyst?
It will be hydrolysed
Draw the gas phase dimer structure of AlCl3 and describe its bonding
It has 2 Al and 6 Cl, each Cl in centre donates a lone pair to the Al. Al is now sp3 hybridised
Describe the solid state structure of AlCl3
It is a polymeric structure with 6 coordinate Al
What does the inert pair effect tell us about the p-block?
it tells us that the stability of the n-2 (n=group no.) oxidation state increases for the heavier elements of group 13, 14 and 15
Describe the reactivity of diborane
It is lewis acidic, it has a +ve formation enthalpy which shows that it is thermodynamically unstable. It is spontaneously flammable in air, and is rapidly hydrolysed by H2O.
What does diborane produce when it reacts in the air?
It produces boric acid (burns with a bright green flame)
Name a use of complex hydrides of group 13
Li[AlH4] and Na[BH4] are used as reducing agents in organic synthesis (very dangerous)
