P block

• The acidic character of trivalent oxide of group 15 element E2O3, decreases down the group.
• Acidic strength of different oxides of same element increases with increase in oxidation state of elemenT
• Boron and silicon and germanium are metalloids
• Arsenic antimony (sb) tellurium and polonium are metalloids
• The occurrence of oxidation states two unit less than the group oxidation states are sometime attributed to the ‘inert pair effect’.
• The first member of p-block differs from the remaining members of their corresponding group in two major respects. First is the size and all other properties which depend on size.

  Thus, the lightest p-block elements show the same kind of differences as the lightest s-block elements, lithium and beryllium. The second important difference, which applies only to the p-block elements, arises from the effect of d-orbitals in the valence shell of heavier elements (starting from the third period onwards) and their lack in second period elements.
• Atomic radii in group 13 goes as B<Ga<Al<In<Tl
• Electronegativity of group 13 B>Al<Ga<In<Tl
• Ionisation energy of group 13 B>Al<Ga>In<Tl
• Boron is unreactive in crystalline form
• Boron does not form dimers due to back bonding

  but aluminium does form dimers
• Maximum covalency of boron is 4
• ALF3 does not exist due to ionic nature
• Aluminium forms are very thin oxide layer on the surface which protects the metal from further attack of oxygen aluminium also reacts with aqueous alkali and liberate dihydrogen
• Boron trioxide is acidic and reacts with basic metallic oxide, forming metal borates
• Boron does not form cations in aqueous solutions and boron only reacts with oxidising acids.

  Boron does not react with water, gallium and indium are not attacked unless oxygen is present tellurium decomposes in red hot steam and oxides in moist air
• Graphite react with concentrated hot red HN03 to form mellitic acid and with HF and HNO3 to form graphite oxide
• Except CCl4 all tetrachlorides are easily hydrolysed by water
• Silicon reacts with magnesium to form magnesium silicate
• Lead is unaffected by water
• Carbon is unaffected by alkali
• Carbon silicon germanium do not react with cold water but carbon does react with steam red hot to produce water gas
• SICL6 does not exist due to size difference and the interaction of lone pair
• Maximum valancy Of carbon is +4
• Dioxide of carbon. Silicon germanium are acidic, whereas oxides of tin and lead are amphoteric
• The oxides of the type E203 of nitrogen and phosphorus are purely acidic, that of arsenic and antimony amphoteric and those of bismuth predominantly basic.
• All these elements form two types of oxides: E203 and E205. The oxide in the higher oxidation state of the element is more acidic than that of lower oxidation state.
• Ammonia is used to produce various nitrogenous fertilisers (ammonium nitrate, urea, ammonium phosphate and ammonium sulphate) and in the manufacture of some inorganic nitrogen compounds, the most important one being nitric acid. Liquid ammonia is also used as a refrigerant.
• the increase in radii is down the group and the ionisation energy as well as electronegativity of increases going up the group of group 15 elements. although the electronegativity of sb and bi is more or less same
• boiling point of sb (antimony) is more than that of bismuth.
• melting point trend of group 13 elements

  N<P<As>sb>bi
• density of group 13 elements increases down the group, nd so does that of group 15 elements but group 14 elements show a slight different trend, carbon is more denser than silicon
• nitrogen exists as a gas whereas all other elements of group 15 exist as a solid. except nitrogen all the elements show allotropy
• The common oxidation states of group 15 elements are –3, +3 and +5. The tendency to exhibit –3 oxidation state decreases down the group due to increase in size and metallic character, bismuth hardly forms any compound in –3 oxidation state. The stability of +5 oxidation state decreases down the group. The only well characterised Bi (V) compound is BiF5 . The stability of +5 oxidation state decreases and that of +3 state increases .
• Nitrogen exhibits + 1, + 2, + 4 oxidation states also when it reacts with oxygen. Phosphorus also shows +1 and +4 oxidation states in some oxoacids.
• In the case of nitrogen, all oxidation states from +1 to +4 tend to disproportionate in acid solution. Similarly, in case of phosphorus nearly all intermediate oxidation states disproportionate into +5 and –3 both in alkali and acid. However +3 oxidation state in case of arsenic, antimony and bismuth becomes increasingly stable with respect to disproportionation.
• grp 15 elements react to form two series of halides: EX3 and EX5. Nitrogen does not form pentahalide due to non-availability of the d orbitals in its valence shell. Pentahalides are more covalent than trihalides. All the trihalides of these elements except those of nitrogen are stable. In case of nitrogen, only NF3 is known to be stable. Trihalides except BiF3 are predominantly covalent in nature.
• grp 15 elements react with metals to form their binary compounds exhibiting –3 oxidation state, such as, Ca3N2 (calcium nitride) Ca3P2 (calcium phosphide), Na3As2 (sodium arsenide), Zn3Sb2 (zinc antimonide) and Mg3Bi2 (magnesium bismuthide
• Unlike NH3 , PH3 molecules are not associated through hydrogen bonding in liquid state. That is why the boiling point of PH3 is lower than NH3 .
• However, the abundance of sulphur in the earth’s crust is only 0.03-0.1%. Combined sulphur exists primarily as sulphates such as gypsum CaSO4 .2H2O, epsom salt MgSO4 .7H2O, baryte BaSO4 and sulphides such as galena PbS, zinc blende ZnS, copper pyrites CuFeS2 . Traces of sulphur occur as hydrogen sulphide in volcanoes. Organic materials such as eggs, proteins, garlic, onion, mustard, hair and wool contain sulphur.