Chemistry of Nonmetals PDF

CHEMISTRY OF NONMETALS  NONMETALS  Nonmetals are (usually) poor conductors of heat and electricity, and are not malleable or ductile; many of the elemental nonmetals are gases at room temperature, while others are liquids and others are solids. The metalloids are intermediate...

CHEMISTRY OF NONMETALS  NONMETALS  Nonmetals are (usually) poor conductors of heat and electricity, and are not malleable or ductile; many of the elemental nonmetals are gases at room temperature, while others are liquids and others are solids. The metalloids are intermediate in their properties. In their physical properties, they are more like the nonmetals, but under certain circumstances, several of them can be made to conduct electricity. These semiconductors are extremely important in computers and other electronic devices NONMETALS  NONMETALS  Approximately 18 elements are classified as nonmetals.  Physical State: Most of the non-metals exist in two of the three states of matter at room temperature: gases (oxygen) and solids (carbon). Only bromine exists as a liquid at room temperature.  Non-Malleable and Ductile: Non-metals are very brittle, and cannot be rolled into wires or pounded into sheets.  Conduction: They are poor conductors of heat and electricity.  Luster: These have no metallic luster and do not reflect light.  Melting and Boiling Points: The melting points of non-metals are generally lower than metals, but are highly variable.  Seven non-metals exist under standard conditions as diatomic molecules: H2(g), N2(g), O2(g), F2(g), Cl2(g), Br2(l), I2(s).  NONMETALS We will concentrate with the more reactive nonmetals: (See Properties of Nonmetallic Elements.pdf)  Nitrogen (N2)and phosphorus(P4) in Group 15  Oxygen(O2) and sulfur(S8) in Group 16  The halogens (F2, Cl2, Br2, I2) in Group 17 NONMETALS  The main group metals are oxidized in all of their chemical reactions. These metals are oxidized when they react with nonmetal elements. Aluminum, for example, is oxidized by bromine. NONMETALS  The chemistry of the nonmetals can undergo both oxidation and reduction. Phosphorus, for example, is oxidized when it reacts with oxygen to form P4O10. NONMETALS  But it is reduced when it reacts with calcium to form calcium phosphide. Periodic table OF ELECTRONEGATIVITY Periodic table OF ELECTRONEGATIVITY  Electronegativity is a measure of an atom's ability to attract the shared electrons of a covalent bond to itself.  ELECTRONEGATIVITY  These reactions can be understood by looking at the relative electronegativities of these elements. 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.  ELECTRONEGATIVITY  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.  ELECTRONEGATIVITY  The behaviour of nonmetals can be summarized as follows:  Nonmetals tends to oxidize metals.  Nonmetals with relatively large electronegativities (such as oxygen and chlorine) oxidize substances with which they react.  Nonmetals with relatively low electronegativities (such as hydrogen and carbon) can reduce other substance. Example 1: HYDROGEN COMPOUNDS of NONMETALS  HYDROGEN COMPOUNDS of NONMETALS  The table below are some important hydrogen compounds of the nonmetals. The physical states listed are those observed at 25ᵒC and 1 atm. GROUP 15 GROUP 16 GROUP 17 Ammonia, NH3(g) Water, H20 (l) Hydrogen fluoride, HF (g) Hydrazine, N2H4(l) Hydrogen peroxide Hydrogen chloride, , H2O2 (l) HCl (g) Hydrazoic acid, HN3(l) Hydrogen sulfide, H2S (g) Hydrogen bromide , HBr (g) Phosphine, PH3 (l) Hydrogen iodide, HI (g) Disphosphine, P2H4(l)  HYDROGEN COMPOUNDS of NONMETALS  Ammonia is used to make fertilizers and a host of different nitrogen compounds. OXYGEN COMPOUNDS of NONMETALS  OXYGEN COMPOUNDS of NONMETALS GROUP 15 GROUP 16 GROUP 17 The states listed are those observe at 25ᵒC and 1 atm. Compounds that decompose below 25ᵒC are listed as (d).  OXYGEN COMPOUNDS of NONMETALS  Nitrogen dioxide, a reddish –brown gas, is a major factor in the formation of photochemical smog.  Chlorine dioxide, a yellow gas, widely used as an industrial bleach and water purifier, even though it tends to explode at partial pressures higher than 50 mmHg.  Nitric oxide, is a minor but villainous component of the atmosphere. It is involved in the formation of both smog and acid rain.  OXYGEN COMPOUNDS of NONMETALS  Small amounts of Nitric oxide are also produced in the human body, where it has generally beneficial effect. It has the ability to dilate blood vessels, lowering blood pressure and reducing the likelihood of strokes or heart attacks.  The best known oxide of nitrogen is nitrous oxide or “ laughing gas”, which is frequently used as an anaesthetic, particularly in dentistry. It is also the propellant gas used in whipped cream containers. Nitrous oxide is nontoxic, virtually tasteless, and quite soluble in vegetable oils. Reactions of Nonmetal Oxides with Water  Reactions of Nonmetal Oxides with Water  Many nonmetal oxides are acidic in the sense that they react with water to form acids.  Phosphoric acid is added in small amounts to soft drinks to give them a tart taste. It is present to the extent of about 0.05 mass percent in colas and 0.01 mass percent in root beers. Example 2 Give the formula of the oxide that reacts with water to form: a. b. c.