GROUP-15 GROUP-15 ELEMENTSELEMENTS

ITROGEN FAMILY

7.1.1 Occurrence

Molecular nitrogen comprises 78% by volume of the atmosphere. In the earth’s crust, it occurs as sodium nitrate, NaNO (called Chile saltpetre) and potassium nitrate (Indian saltpetre). It is found in the form of proteins in plants and animals. Phosphorus occurs in minerals of the apatite family, which are the main components of phosphate rocks. Phosphorus is an essential constituent of animal and plant matter. It is present in bones as well as in living cells. Phosphoproteins are present in milk and eggs. Arsenic, antimony and bismuth are found mainly as sulphide minerals.

INTRODUCTIONINTRODUCTION

ATOMIC AND PHYSICAL PROPERTIES OF GROUP 15 ELEMENTS

Electronegativity (the atom's ability of attracting electrons) increases up the group.

Ionization Energy (the amount of energy required to remove an electron from the atom in it's gaseous phase) increases up the group.

Atomic Radii (the radius of the atom) increases down the group.  Electron Affinity (ability of the atom to accept an electron) increases going up the group.

Melting Point (amount of energy required to break bonds to change a solid phase substance to a liquid phase) increases going down the group.

Boiling Point (amount of energy required to break bonds to change a liquid phase substance to a gas) increases going down the group. 

Metallic Character (how metallic the atom is) increases going down the group. 

Electronic Configuration. The valence shell electronic configuration of these elements is ns2np3. The s orbital in these elements is completely filled and p orbitals are half-filled, making their electronic configuration extra stable.

Atomic and Ionic Radii. Covalent and ionic (in a particular state) radii increase in size down the group. There is a considerable increase in covalent radius from N to P. However, from As to Bi only a small increase in covalent radius is observed. This is due to the presence of completely filled d and/or f orbitals in heavier members.

TRENDS IN PROPERTIES

SOME IMPORTANT GROUP – 15 ELEMENTS

NITROGEN NITROGEN

AND AND

PHOSPHORUSPHOSPHORUS

NITROGEN NITROGEN

AND AND

PHOSPHORUSPHOSPHORUS

Nitrogen is a chemical element with symbol N and atomic number 7. Elemental nitrogen is a Nitrogen is a chemical element with symbol N and atomic number 7. Elemental nitrogen is a colourless, odourless, tasteless, and mostly inert diatomic gas at Std. conditions constituting colourless, odourless, tasteless, and mostly inert diatomic gas at Std. conditions constituting 78.09% by volume of Earth’s Atmosphere. The element nitrogen was discovered as a 78.09% by volume of Earth’s Atmosphere. The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford , in 1772..separable component of air, by Scottish physician Daniel Rutherford , in 1772..Nitrogen occurs in all organisms, primarily in amino acids  and also in the  nucleic acids. The Nitrogen occurs in all organisms, primarily in amino acids  and also in the  nucleic acids. The human body contains about 3% by weight of nitrogen, the fourth most abundant element in human body contains about 3% by weight of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. the body after oxygen, carbon, and hydrogen. ProductionProductionNitrogen gas is an industrial gas  produced by the fractional distillation of liquid air , or by Nitrogen gas is an industrial gas  produced by the fractional distillation of liquid air , or by mechanical means using gaseous air (i.e., pressurized reverse osmosis membrane. In a mechanical means using gaseous air (i.e., pressurized reverse osmosis membrane. In a chemical laboratory it is prepared by treating an aqueous solution of ammonium chloride chemical laboratory it is prepared by treating an aqueous solution of ammonium chloride with sodium nitrite NH4Cl(aq) + NaNO2(aq) → N2(g) + NaCl(aq) + 2 H2O (l)with sodium nitrite NH4Cl(aq) + NaNO2(aq) → N2(g) + NaCl(aq) + 2 H2O (l)Small amounts of impurities NO and HNO3 are also formed in this reaction. The impurities Small amounts of impurities NO and HNO3 are also formed in this reaction. The impurities can be removed by passing the gas through aqueous sulfuric acid containing potassium can be removed by passing the gas through aqueous sulfuric acid containing potassium dichromate  Very pure nitrogen can be prepared by the thermal decomposition of barium dichromate  Very pure nitrogen can be prepared by the thermal decomposition of barium azide   2 NaN3 → 2 Na + 3 N2azide   2 NaN3 → 2 Na + 3 N2  PropertiesPropertiesNitrogen is a non-metal with an electronegativity of 3.04. It has five electrons in its outer Nitrogen is a non-metal with an electronegativity of 3.04. It has five electrons in its outer shell and is, therefore, trivalent in most compounds. The triple bond in molecular nitrogen shell and is, therefore, trivalent in most compounds. The triple bond in molecular nitrogen (N2) is one of the strongest. The resulting difficulty of converting N2 into other compounds, (N2) is one of the strongest. The resulting difficulty of converting N2 into other compounds, and the ease (and associated high energy release) of converting nitrogen compounds into and the ease (and associated high energy release) of converting nitrogen compounds into elemental N2, have dominated the role of nitrogen in both nature and human economic elemental N2, have dominated the role of nitrogen in both nature and human economic activities.activities.At atmospheric pressure molecular nitrogen condenses (liquefies) at 77 K (−195.79 °C) At atmospheric pressure molecular nitrogen condenses (liquefies) at 77 K (−195.79 °C) and freezes at 63 K (−210.01 °C) into the beta hexagonal close-packed and freezes at 63 K (−210.01 °C) into the beta hexagonal close-packed crystal allotropic form. Below 35.4 K (−237.6 °C) nitrogen assumes the cubic crystal crystal allotropic form. Below 35.4 K (−237.6 °C) nitrogen assumes the cubic crystal allotropic form (called the alpha phase). Liquid nitrogen a fluid resembling water in allotropic form (called the alpha phase). Liquid nitrogen a fluid resembling water in appearance, but with 80.8% of the density (the density of liquid nitrogen at its boiling point appearance, but with 80.8% of the density (the density of liquid nitrogen at its boiling point is 0.808 g/mL), is a common cryogen.is 0.808 g/mL), is a common cryogen.

NITROGEN

  REACTIONSREACTIONSStructure of dinitrogen, NStructure of dinitrogen, N2 2 in general, nitrogen is unreactive at standard in general, nitrogen is unreactive at standard temperature and pressure. Ntemperature and pressure. N22 reacts spontaneously with fewre agents, being  reacts spontaneously with fewre agents, being resilient to acids and bases as well as oxidants and most reductants. When resilient to acids and bases as well as oxidants and most reductants. When nitrogen reacts spontaneously with a reagent, the net transformation is often nitrogen reacts spontaneously with a reagent, the net transformation is often called nitrogen fixation. Nitrogen reacts with elemental lithium. Lithium burns in called nitrogen fixation. Nitrogen reacts with elemental lithium. Lithium burns in an atmosphere of Nan atmosphere of N22 to give lithium nitride. 6 LI + N to give lithium nitride. 6 LI + N22 → 2 LI → 2 LI33N magnesium also N magnesium also burns in nitrogen, forming magnesium nitride. 3 MG + Nburns in nitrogen, forming magnesium nitride. 3 MG + N22 → MG → MG33NN22

COMPOUNDSCOMPOUNDSTThe main neutral hydride of nitrogen is ammonia (NH3), he main neutral hydride of nitrogen is ammonia (NH3), although hydrazine (N2H4) is also commonly used. ammonia is more basic than although hydrazine (N2H4) is also commonly used. ammonia is more basic than water by 6 orders of magnitude. in solution ammonia forms water by 6 orders of magnitude. in solution ammonia forms the ammonium ion (NH4the ammonium ion (NH4++). liquid ammonia (boiling point 240 K) IS ). liquid ammonia (boiling point 240 K) IS amphiprotic (displaying either brønsted-lowry acidic or basic character) and amphiprotic (displaying either brønsted-lowry acidic or basic character) and forms ammonium . singly, doubly, triply and quadruply substituted alkyl forms ammonium . singly, doubly, triply and quadruply substituted alkyl compounds of ammonia are called amines (four substitutions, to form compounds of ammonia are called amines (four substitutions, to form commercially and biologically important quaternary amines, results in a commercially and biologically important quaternary amines, results in a positively charged nitrogen, and thus a water-soluble, or at least amphiphilic, positively charged nitrogen, and thus a water-soluble, or at least amphiphilic, compound). larger chains, rings and structures of nitrogen hydrides are also compound). larger chains, rings and structures of nitrogen hydrides are also known, but are generally unstable.known, but are generally unstable.the higher oxides dinitrogen trioxide N2O3, dinitrogen the higher oxides dinitrogen trioxide N2O3, dinitrogen tetroxide N2O4 AND dinitrogen pentoxide N2O5, are unstable and explosive, a tetroxide N2O4 AND dinitrogen pentoxide N2O5, are unstable and explosive, a consequence of the chemical stability of N2. nearly every hypergolic rocket consequence of the chemical stability of N2. nearly every hypergolic rocket engine uses N2O4 as the oxidizer; their fuels, various forms of hydrazine, are engine uses N2O4 as the oxidizer; their fuels, various forms of hydrazine, are also nitrogen compounds. these engines are extensively used on spacecraft such also nitrogen compounds. these engines are extensively used on spacecraft such as the space shuttle and those of the Apollo program because their propellants as the space shuttle and those of the Apollo program because their propellants are liquids at room temperature and ignition occurs on contact without an are liquids at room temperature and ignition occurs on contact without an ignition system, allowing many precisely controlled burns.ignition system, allowing many precisely controlled burns.

Phosphorus is a nonmetallic chemical element with symbol P and atomic number 15., phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks. Elemental phosphorus exists in two major forms—white phosphorus and red phosphorus but due to its high reactivity, phosphorus is never found as a free element on Earth. Forms of phosphorus and their properties

OccurrencePhosphorus is not found free in nature, but is widely distributed in many minerals, mainly phosphates. Histo -rically-important but limited commercial sources were organic, such as bone ash and (in 19 th century) guano. Inorganic phosphate rock, which is partially made of apatite (an impure tri-calcium phosphate mineral), is today the chief commercial source of this element. About 50 % of the global phosphorus reserves are in the Arab nations. 

ApplicationsFertilizerThe dominant application of phosphorus is in fertilizers, which provides phosphate as required for all life and is often a limiting nutrient for crops. Phosphorus, being an essential plant nutrient, finds its major use as a constituent of fertilizers for agriculture and farm production in the form of concentrated phosphoric acids, which can consist of 70% to 75% P2O5. Due to the essential nature of phosphorus to living organisms, the low

solubility of natural phosphorus-containing compounds, and the slow natural cycle of phosphorus, the agricultural industry relies on fertilizers that contain phosphate.

Water softeningSodium tripolyphosphate made from phosphoric acid is used in laundry detergents in some countries, but banned for this use in others. It is useful for softening water to enhance the performance of the detergents and to prevent pipe/boiler tube corrosion

PHOSPHORUS

COMPOUNDS OF PHOSPHORUS COMPOUNDS OF PHOSPHORUS

The EndThe End

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