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Chemistry of Nonmetals
1Dr.Riham Hazzaa
OXIDATION-REDUCTION REACTIONS
• A redox reaction involves the transfer of electrons between reactants
• Electrons gained by one species must equal electrons lost by another
• Both oxidation and reduction must occur simultaneously.
• Oxidation: removal of electrons • Reduction: gain of electrons
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2Dr.Riham Hazzaa
• oxidising and reducing agents• An oxidizing agent is an element which causes
oxidation (and is reduced as a result) by removing electrons from another species. oxidizing agent is the electron acceptor
• A reducing agent is an element which causes reduction (and is oxidized as a result) by giving electrons to another species. reducing agent is the electron donor.
Na(s) + Cl (g) → NaCl(s)
3Dr.Riham Hazzaa
The main group metals are oxidized in all of their chemical reactions. These metals are oxidized when they react with nonmetal elements.
4Dr.Riham Hazzaa
• Nonmetals can undergo both oxidation and reduction.
• Phosphorus, is oxidized when it reacts with oxygen to form P4O10.
• it is reduced when it reacts with calcium to form calcium phosphide.
5Dr.Riham Hazzaa
• Phosphorus (EN = 2.19) is less electronegative than oxygen (EN = 3.44). When these elements react, the electrons are drawn toward the more electronegative oxygen atoms. Phosphorus is therefore oxidized in this reaction, and oxygen is reduced.
• Calcium (EN = 1.00), on the other hand, is significantly less electronegative than phosphorus (EN = 2.19). When these elements react, the electrons are drawn toward the more electronegative phosphorus atoms. As a result, calcium is oxidized and phosphorus is reduced.
6Dr.Riham Hazzaa
The behavior of the nonmetals• Nonmetals tend to oxidize metals.
• Nonmetals with relatively large electronegativities (such as oxygen and chlorine) oxidize substances with which they react.
• Nonmetals with relatively small electronegativities (such as carbon and hydrogen) can reduce other substances.
2 Mg(s)+O2(g)→2 MgO(s)
2 H2S(g)+3 O2(g)→2 SO2(g)+2 H2O(g)
CuO(s)+ H2(g)→Cu(s)+H2O(g)
7Dr.Riham Hazzaa
Hydrogen• Compounds of hydrogen are frequently called
hydrides, even though the name hydride describes compounds that contain an H- ion.
H+=1s0
H=1s1
H-=1s2
8Dr.Riham Hazzaa
• Because hydrogen forms compounds with oxidation numbers of both +1 and -1, many periodic tables include this element in both Group IA (with Li, Na, K, Rb, Cs, and Fr) and Group VIIA (with F, Cl, Br, I).
• The first ionization energy of hydrogen (1312 kJ/mol), is halfway between the elements with the largest (2372 kJ/mol) and smallest (376 kJ/mol) ionization energies.
• Hydrogen has an electronegativity (EN = 2.20) halfway between the extremes of the most electronegative (EN = 3.98) and least electronegative (EN = 0.7) elements. 9
Dr.Riham Hazzaa
• Hydrogen is oxidized by elements that are more electronegative to form compounds in which it has an oxidation number of +1.
• Hydrogen is reduced by elements that are less electronegative to form compounds in which its oxidation number is -1.
10Dr.Riham Hazzaa
Formation of Hydrogen• By reacting an active metal with water.
• By reacting a less active metal with a strong acid.
2 Na(s)+2 H2O(l)2 Na+(aq)+2 OH-(aq)+H2(g)↑
Zn(s) +2 HCl(aq)Zn2+(aq)+2 Cl-(aq)+ H2(g)↑
11Dr.Riham Hazzaa
• By reacting an ionic metal hydride with water
• By decomposing water into its elements with an electric current.
NaH(s)+H2O(l)Na+(aq)+OH-(aq)+H2(g)
electrolysis
2 H2O(l) 2 H2(g)+O2(g)
12Dr.Riham Hazzaa
The Chemistry of Nitrogen (GroupV)
• A neutral nitrogen atom contains five valence electrons: 2s2 2p3.
• Because the covalent radius of a nitrogen atom is relatively small (only 0.070 nm), nitrogen atoms come close enough together to form very strong bonds.
• The strength of the nitrogen-nitrogen triple bond makes the N2 molecule very unreactive.
13Dr.Riham Hazzaa
The Synthesis of Ammonia NH3 Haber process
• The Haber process, a mixture of N2 and H2 gas at 200 to 300 atm and 400 to 600oC is passed over a catalyst of finely divided iron metal.
• Two-thirds of the ammonia used for fertilizers is converted into solids such as ammonium nitrate, NH4NO3; ammonium phosphate, (NH4)3PO4; ammonium sulfate, (NH4)2SO4; and urea, H2NCONH2. The other third is applied directly to the soil as anhydrous ammonia.
Fe
N2(g)+3 H2(g)2 NH3(g)
14Dr.Riham Hazzaa
• The Synthesis of Nitric Acid Ostwald process
4 NH3(g)+5 O2(g)4 NO(g)+6 H2O(g)
2 NO(g)+O2(g)2 NO2(g)
3 NO2(g)+ H2O(l)2 HNO3(aq)+NO(g)
15Dr.Riham Hazzaa
The Nitrogen Oxides 1. Dinitrogen oxide, N2O which is also known as
nitrous oxide, can be prepared by carefully decomposing ammonium nitrate.
170 to 200oC
NH4NO3(s)N2O(g)+2 H2O(g)
16Dr.Riham Hazzaa
2. Nitrogen oxide, or nitric oxide,
Nitrogen oxide NO can be prepared in the laboratory by reacting copper metal with dilute nitric acid.
N2(g) +O2(g)2 NO(g)
3 Cu(s)+8 HNO3(aq) 3 Cu(NO3)2(aq)+2 NO(g)+4 H2O(l)
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3. Nitrogen dioxide NO2
NO reacts rapidly with O2 to form nitrogen dioxide (once known as nitrogen peroxide), which is a dark brown gas at room temperature.
It can also be made by reacting copper metal with
concentrated nitric acid,
2 NO(g)+O2(g)2 NO2(g)
Cu(s)+4 HNO3(aq)Cu(NO3)2(aq)+2 NO2(g)+2 H2O(l)
18Dr.Riham Hazzaa
4. Dinitrogen pentoxide By carefully removing water from concentrated
nitric acid at low temperatures with a dehydrating agent we can form dinitrogen pentoxide.
4 HNO3(aq)+P4O10(s)2 N2O5(s) +4 HPO3(s)
19Dr.Riham Hazzaa