Chemistry of Non-Metals Lesson 25 by Owen Borville 11.11.2025
The Chemistry of Non-Metal Elements and Compounds
Nonmetals are found in the upper and right side of the Periodic Table of the Elements, in addition to hydrogen on the left side.
Properties of nonmetals are more varied than those of metals. Hydrogen, oxygen, nitrogen, fluorine, chlorine, and the noble gases are all gases in the elemental state. Only bromine is a liquid and all other nonmetals are solids at room temperature.
Metalloids have properties characteristic of both metals and nonmetals. Boron, silicon, germanium, and arsenic are semiconducting elements. Nonmetals are more electronegative than metals. Compounds formed by a combination of metals with nonmetals tend to be ionic, having a metallic cation and a nonmetallic anion.
Hydrogen is the simplest element known. The most common atomic form contains only one proton and one electron. The atomic form exists only at very high temperatures. Normally, elemental hydrogen is a diatomic molecule.
Molecular hydrogen is a colorless, odorless, and nonpoisonous gas. At 1 atm, hydrogen has a boiling point of -252.9 degrees C.
Hydrogen is the most abundant element in the universe (70 percent of total mass).
Hydrogen is the 10th most abundant element in Earth's crust, found in combination with other elements.
Ground state electron configuration of H is 1s1.
Hydrogen resembles alkali metals and it can be oxidized to the H+ ion, which exists in aqueous solutions in the hydrated form.
Hydrogen also resembles halogens and forms the hydride ion.
Hydrogen is found in a large number of covalent compounds.
When bonded to small, electronegative atoms, hydrogen has the unique capacity to form hydrogen bonds.
Hydrogen gas is important to industrial processes. The large-scale industrial preparation of hydrogen gas from propane gas and steam in the presence of a catalyst at 900 degrees C: C3H8(g) + 3H2O(g) => 3CO(g) + 7H2(g)
In another process, steam is passed over a bed of red-hot coke:
C(s) + H2O(g) =>CO(g) + H2(g)
Small quantities of hydrogen gas can be prepared in the laboratory by combining zinc metal with dilute hydrochloric acid:
Zn(s) + 2HCl(aq) => ZnCl2(aq) + H2(g)
Binary hydrides are compounds containing hydrogen and another element, either a metal or a nonmetal. Three types of binary hydrides are (1) ionic hydrides (2) covalent hydrides (3) interstitial hydrides
Ionic hydrides are formed when molecular hydrogen combines directly with any alkali metal or with alkaline earth metals Ca, Sr, or Ba:
2Li(s) + H2(g) => 2LiH(s)
Ca(s) + H2(g) => CaH3(s)
Ionic hydrides have high melting points characteristic of ionic compounds. The anion in these compounds is the hydride ion (H-) , which is a very strong Bronsted base:
H-(aq) + H2O(l) => OH-(aq) + H2(g)
Because of their high reactivity with water, ionic hydrides are frequently used to remove traces of water from organic solvents.
In covalent hydrides, the hydrogen atom is covalently bonded to the atom of another element. Two types of covalent hydrides: (1) with discrete molecular units (2) with complex polymeric structures.
Molecular hydrogen forms a number of hydrides with transition metals. In some of these compounds, the ratio of hydrogen atoms to metal atoms is not a constant. Such compounds are called interstitial hydrides (metallic hydrides) form when hydrogen atoms occupy empty spaces in the crystal lattice of transition metals.
Depending on the conditions, for example, the formula for titanium hydride can vary between TiH1.8 and TiH2.
Many of the interstitial hydrides have metallic properties such as electrical conductivity. Hydrogen is known to be bonded to the metal, although the exact nature of the bonding is usually unclear.
Isotopes of hydrogen include hydrogen-1 with one neutron, hydrogen-2 deuterium (D) with two neutrons, and hydrogen-3 tritium (T) with three neutrons. All of these have one proton.
D2O (deuterium oxide) resembles H2O chemically in most respects, but it is still a toxic substance. Deuterium is heavier than hydrogen-1, so its compounds react more slowly than those of the lighter isotope. Deuterium oxide is heavier, denser, and has higher melting and boiling points than H2O.
The kinetic isotope effect is seen with acid ionization constants (Ka) For example, replacing CH3COOH(aq) with CH3COOD(aq) will make the dissociation reaction three times slower for D+ than H+.
Hydrogenation is the addition of hydrogen to compounds containing multiple bonds, usually C=C double and triple bonds. The process under normal conditions is slow and the rate may be increased by using a metal catalyst and a higher temperature and pressure.
Hydrogen gas is being researched as an alternative energy source. Hydrogen gas could replace gasoline to power automobiles or be used with oxygen gas in fuel cells to generate electricity. H2 reactions are mostly void of pollutants and the final product formed in hydrogen-powered engines or fuel cells would be water: 2H2(g) + O2(g) => 2H2O(l). The challenges of hydrogen gas to be successful as alternative energy would be the affordability of production costs and the ease of storage methods.
Carbon is an essential element of living matter, but only 0.09 percent by mass of the Earth's crust. Carbon is found in the form of diamond and graphite, and natural gas, petroleum, and coal. Carbon combines with oxygen to form carbon dioxide (CO2) in the atmosphere and occurs as carbonate [CO3(2-)] in limestone and chalk rock.
Diamond and graphite are allotropes (distinct physical forms) of carbon. Although graphite is the stable form of carbon at 1 atm and 25 degrees C, the rate of spontaneous process from diamond to graphite is very slow (ΔG°= -2.87 kJ/mol).
Synthetic diamond can be produced from graphite by applying very high pressure and temperature in the laboratory.
Carbon has a unique ability to form long chains containing more than 50 carbon atoms and stable rings with five or six members. This phenomenon of linking like atoms is called catenation. Carbon's versatility allows for millions of organic compounds on Earth.
Carbides form when carbon combines with metals to form ionic compounds, such as CaC2, BeC2, SiC, Fe3C, where carbon is in the form of (C2)2- or (C)4-. These carbon ions make strong Bronsted bases and react with water to form hydroxide ions and C2H2 and CH4 respectively.
Carborundum forms when carbon forms a covalent compound with silicon (SiC): SiO2(s) + 3C(s) => SiC(s) + 2CO(g). Carborundum is almost as hard as diamond and is used industrially mainly for cutting, grinding, and polishing metals and glasses.
Cyanides are another class of carbon compounds that contain the anion group: CN-(triple bonded). Cyanides are very toxic to humans and animals because they bind to the cytochrome oxidase, an important enzyme in the metabolic process of aerobic respiration, and halt the process. Hydrogen cyanide (HCN) is even more dangerous because of its volatility and quicker reaction. Cyanide ions are also used in mining to dissolve and extract gold and silver from the ore.
Carbon monoxide (CO) and carbon dioxide (CO2) are the most important carbon oxides. Carbon monoxide is a colorless, odorless gas formed by the incomplete combustion of carbon or carbon-containing compounds: 2C(s) + O2(g) => 2CO(g) Carbon monoxide is used in metallurgical processes, it is not an acidic oxide, and it is only slightly soluble in water. Carbon dioxide is a colorless, odorless gas and is non-toxic. It is a simple asphyxiant and is used in fire extinguishers. Solid CO2 (dry ice) is used as a refrigerant.
Nitrogen is about 78 percent of air by volume. Nitrogen is an essential element of life because it is a component of proteins and nucleic acids. The N2 molecule contains a triple bond and is very stable with respect to dissociation into atomic species. Nitrogen forms a large number of compounds with hydrogen and oxygen in which the oxidation number varies from -3 to +5. Most nitrogen compounds are covalent. When heated with metals, however, nitrogen forms ionic nitrides containing the N3- ion.
The nitride ion (N3-) is a very strong Bronsted base and reacts with water to produce ammonia and hydroxide ion. Ammonia is a colorless gas with an irritating odor and is used in fertilizers. Hydrazine is another hydride of nitrogen, a colorless liquid that smells like ammonia, and a base used as a reducing agent. Hydrazine has a role in polymer synthesis and in the manufacture of pesticides.
Nitrous oxide (N2O) is a colorless gas with a pleasing odor and sweet taste. N2O resembles molecular oxygen in that it supports combustion because it decomposes when heated to form molecular nitrogen and molecular oxygen. Nitrous oxide is used in dental procedures and other minor surgery (laughing gas).
Nitric oxide (NO) is a colorless gas and is paramagnetic molecule containing one unpaired electron.
Nitrogen dioxide (NO2) is a highly toxic yellow-brown gas with a choking odor. Nitrogen dioxide is paramagnetic, and has a strong tendency to dimerize into dinitrogen tetroxide (N2O4), which is diamagnetic. Nitrogen dioxide is an acidic oxide and it reacts rapidly with cold water to form both nitrous acid (HNO2) and nitric acid (HNO3).
Nitric acid (HNO3) is one of the most important inorganic acids. Nitric acid is a liquid, but does not exist as a pure liquid because it decomposes suddenly to NO2, H2O and O2. Nitric acid is a powerful oxidizing agent and it can oxidize metals both above and below hydrogen in the activity series. Nitric acid is also used in the manufacture of fertilizers, dyes, drugs, and explosives.
Phosphorus (Group 5A element) occurs most commonly in nature as phosphate rocks, which are mostly calcium phosphate and fluoroapatite. Elemental phosphorus can be isolated by heating solid calcium phosphate (Ca3(PO4)2) with coke (solid carbon) and solid silica sand (SiO2), which produces solid CaSiO3, CO gas, and isolated solid phosphorus (P4). There are several allotropic forms of phosphorus, white (used in explosives), red (used in matches), and black phosphorus (used in electronics).
White phosphorus contains tetrahedral P4 molecules. It is insoluble in water but very soluble in carbon disulfide (CS2) and organic solvents such as chloroform (CHCl3). White phosphorus is highly toxic and bursts into flames spontaneously when exposed to air: P4(s) + 5O2(g) => P4O10 (s).
When heated in the absence of air, white phosphorus is slowly converted to red phosphorus at about 300 degrees C: P4 (white phosphorus) => P4 (red phosphorus). Red phosphorus has a polymeric structure and is more stable and less volatile than white phosphorus.
Phosphine (PH3) is the most important hydride of phosphorus. PH3 is a colorless, very poisonous gas formed by heating white phosphorus in concentrated sodium hydroxide. Phosphine is moderately soluble in water and more soluble in carbon disulfide and organic solvents. Phosphine is a strong reducing agent and it reduces many metal salts to the corresponding metals. Phosphine gas burns in air: PH3(g) + 2O2(g) => H3PO4(s).
Phosphorus forms binary compounds with halogens-namely, the trihalides (PX3) and the pentahalides (PX5). The two imp0rtant oxides of phosphorus are tetraphosphorus hexoxide (P4O6) and tetraphosphorus decoxide (P4O10). The oxides are isolated by burning white phosphorus in limited and excess amounts of oxygen gas, respectively.
P4(s) + 3O2(g) => P4O6(s)
P4(s) + 5O2(g) => P4O10(s)
Both oxides are converted to acids in water. The compound P4O10 is a white flocculent powder that has a great affinity for water: P4O6(s) + 6H2O(l) => 4H3PO4(aq). For this reason, P4O10 is often used for drying gases and for removing water from solvents.
There are many oxoacids containing phosphorus: Phosphorus acid (H3PO3), Hypophosphorous acid (H3PO2), Phosphoric acid (H3PO4), and Triphosphoric acid (H5P3O10).
Phosphoric acid and phosphates have many commercial applications in detergents, fertilizers, flame retardants, and toothpastes, and as buffers in carbonated beverages.
Phosphorus is an element that is essential for life. Phosphorus is only about 1 percent by mass of the human body. However, the human skeleton is 23 percent mineral matter, the phosphorus content of which (calcium phosphate), is 20 percent. Phosphates are also important components of the genetic material in DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Oxygen is the most abundant element in the Earth's crust (46 percent of mass). In addition, the atmosphere is about 21 percent molecular oxygen by volume as a diatomic molecule (O2). Oxygen is a building block of almost all biomolecules (25 percent of all biomatter). Molecular oxygen is the essential oxidant in the metabolic breakdown of food molecules.
Oxygen (O2) has one other allotrope, (O3, ozone) which is less stable than O2. The O2 molecule is paramagnetic with two unpaired electrons. Molecular oxygen is a strong oxidizing agent and is one of the most widely used industrial chemicals. Oxygen forms three types of oxides: oxide (O2-), peroxide [(O2)2-], and superoxide (O2-). The ions are all strong Bronsted bases and react with water:
Oxide: O2-(aq) + H2O(l) => 2OH-(aq) (hydrolysis reaction)
Peroxide: 2(O2)2-(aq) + 2H2O(l) => O2(g) + 4OH- (redox reaction)
Superoxide: 4(O2)-(aq) + 2H2O(l) => 3O2(g) + 4OH-(aq) (redox reaction)
The nature of bonding in oxides changes across any period in the periodic table, from basic oxides (Na2O, CaO, MgO, FeO), to amphoteric (acid or base, Al2O3, ZnO), to acidic oxides (SO2, SO3, CO2, N2O5, N2O3, P4O10). The basicity of the oxides increases as we move down a particular group of the Periodic Table, and acidity decreases as we move down a group.
Hydrogen Peroxide (H2O2) is a colorless viscous (thick) liquid chemical used for cleaning, disinfecting, and bleaching. Hydrogen peroxide readily decomposes when heated or exposed to sunlight into liquid water and O2 gas. 2H2O2(l) => 2H2O(l) + O2(g) ΔH°=-196.4 kJ/mol. This is a disproportionation reaction=a redox reaction where a single element in one reactant simultaneously undergoes both oxidation (loses electrons) and reduction (gains electrons) to form two different products because the element is an intermediate oxidation state and can both increase and decrease its oxidation number. The oxidation number of oxygen changes from 1- to -2 and 0.
Dilute hydrogen peroxide solutions (3% by mass) are used as mild antiseptics and more concentrated H2O2 solutions are used as bleaching agents. The high heat of decomposition also makes hydrogen peroxide a suitable component in rocket fuel.
Ozone is a toxic, light-blue gas and its strong odor is noticeable around electrical discharges and after lightning strikes. Ozone is less stable than molecular oxygen. The ozone molecule has a bent structure with three oxygen atoms, one at each end and one at the bend, two atoms of which are double bonded and the other oxygen is single bonded. Ozone is used to purify water, deodorize air and sewage gases, and to bleach waxes, oils, and textiles. Ozone oxidizes all common metals except gold and platinum. 3O2 =>2O3 (g) ΔG∘ = 326.8 kJ/mol is the change in Gibbs Free Energy needed to convert O2 to O3.
Sulfur occurs in nature in elemental form and the largest known reserves are found in sedimentary deposits, including gypsum and sulfide minerals including pyrite, and natural gas as H2S and SO2.
Allotropes of sulfur are rhombic and monoclinic forms. Rhombic sulfur is thermodynamically the most stable form and it has an atomic ring structure (S8) that is wrinkled in shape. Sulfur is yellow, tasteless, and odorless solid insoluble in water but soluble in carbon disulfide. When heated, it is slowly converted to monoclinic sulfur, which also consists of S8 units. When sulfur is heated above 150 degrees, the rings break up. Sulfur has several oxidation numbers, from -2, 0, +1, +2, +4, +6.
Hydrogen sulfide (H2S) is a colorless gas that smells like rotten eggs and it is highly toxic because it attacks the respiratory system in humans and animals. Sulfur oxides are sulfur dioxide (SO2) and sulfur trioxide (SO3). Sulfur dioxide has a strong smell and is a colorless gas that is very toxic. SO2 can be oxidized to sulfur trioxide. 2SO2(g) + O2(g) => 2SO3(g).
Sulfur trioxide dissolves in water to form sulfuric acid: SO3(g) + H2O(l)=> H2SO4(g). Sulfuric acid is one of the most important industrial chemicals. Sulfuric acid is a diprotic acid, colorless, thick, viscous fluid. Laboratory sulfuric acid is 98 percent H2SO4. Concentrated sulfuric acid oxidizes metals.
Carbon disulfide (CS2) is a two-double bond structure molecule, colorless, flammable liquid formed by heating carbon and sulfur to a high temperature. C(s) + 2S(l) =>CS2(l).
Sulfur hexafluoride (SF6) is a nontoxic, colorless gas, and the most inert of all sulfur compounds.
Halogens: Fluorine, chlorine, bromine, and iodine are reactive nonmetals. Fluorine is the most reactive of all the halogens. Hydrogen fluoride (HF) has a high boiling point of 19.5 degrees C as a result of strong intermolecular hydrogen bonding, but other hydrogen halides have lower boiling points. Hydrofluoric acid (HF dissolved in water) is a weak acid, but all other hydrohalic acids (HCl, HBr, and HI) are strong acids. Fluorine reacts with cold sodium hydroxide solution to produce oxygen difluoride. Silver fluoride (AgF) is soluble, but all other silver halides are insoluble.
Fluorine and chlorine are strong oxidizing agents and must be prepared by electrolysis. The hydrogen halides can be formed by the direct combination of elements: H2(g) + X2(g) => 2HX(g), where X represents a halogen and the reactions can occur explosively.
In the laboratory, hydrogen fluoride and hydrogen chloride can be prepared by combining the metal halide with concentrated sulfuric acid:
CaF2(s) + H2SO4(aq) => 2HF(g) + CaSO4(s)
2NaCl(s) + H2SO4(aq) =>2HCl(g) + Na2SO4(aq)
HF is very highly reactive and its attacks silica, so it is used for etching glass.
Aqueous solutions of hydrogen halides are acidic and the strength of the acids increases from: HF << HCl< HBr< HI.
The halogens also form a series of oxoacids with the general formulas: HXO (hypohalous acid), HXO2 (halous acid), HXO3 (halic acid), HXO4 (perhalic acid), where X represents a halogen element.
NaF is used in drinking water to reduce dental caries (cavities). UF6 is used to separate U-235 and U-238 isotopes. Fluorine F is used to produce the polymer Teflon. Chlorine Cl works in the human body as the principle anion in intracellular and extracellular fluids. Chlorine is also used to purify water. Silver bromide AgBr is used in photographic films. Iodine is used in medicine as an antiseptic. Silver Iodide AgI is used in cloud seeding to induce rainfall.
The Chemistry of Non-Metal Elements and Compounds
Nonmetals are found in the upper and right side of the Periodic Table of the Elements, in addition to hydrogen on the left side.
Properties of nonmetals are more varied than those of metals. Hydrogen, oxygen, nitrogen, fluorine, chlorine, and the noble gases are all gases in the elemental state. Only bromine is a liquid and all other nonmetals are solids at room temperature.
Metalloids have properties characteristic of both metals and nonmetals. Boron, silicon, germanium, and arsenic are semiconducting elements. Nonmetals are more electronegative than metals. Compounds formed by a combination of metals with nonmetals tend to be ionic, having a metallic cation and a nonmetallic anion.
Hydrogen is the simplest element known. The most common atomic form contains only one proton and one electron. The atomic form exists only at very high temperatures. Normally, elemental hydrogen is a diatomic molecule.
Molecular hydrogen is a colorless, odorless, and nonpoisonous gas. At 1 atm, hydrogen has a boiling point of -252.9 degrees C.
Hydrogen is the most abundant element in the universe (70 percent of total mass).
Hydrogen is the 10th most abundant element in Earth's crust, found in combination with other elements.
Ground state electron configuration of H is 1s1.
Hydrogen resembles alkali metals and it can be oxidized to the H+ ion, which exists in aqueous solutions in the hydrated form.
Hydrogen also resembles halogens and forms the hydride ion.
Hydrogen is found in a large number of covalent compounds.
When bonded to small, electronegative atoms, hydrogen has the unique capacity to form hydrogen bonds.
Hydrogen gas is important to industrial processes. The large-scale industrial preparation of hydrogen gas from propane gas and steam in the presence of a catalyst at 900 degrees C: C3H8(g) + 3H2O(g) => 3CO(g) + 7H2(g)
In another process, steam is passed over a bed of red-hot coke:
C(s) + H2O(g) =>CO(g) + H2(g)
Small quantities of hydrogen gas can be prepared in the laboratory by combining zinc metal with dilute hydrochloric acid:
Zn(s) + 2HCl(aq) => ZnCl2(aq) + H2(g)
Binary hydrides are compounds containing hydrogen and another element, either a metal or a nonmetal. Three types of binary hydrides are (1) ionic hydrides (2) covalent hydrides (3) interstitial hydrides
Ionic hydrides are formed when molecular hydrogen combines directly with any alkali metal or with alkaline earth metals Ca, Sr, or Ba:
2Li(s) + H2(g) => 2LiH(s)
Ca(s) + H2(g) => CaH3(s)
Ionic hydrides have high melting points characteristic of ionic compounds. The anion in these compounds is the hydride ion (H-) , which is a very strong Bronsted base:
H-(aq) + H2O(l) => OH-(aq) + H2(g)
Because of their high reactivity with water, ionic hydrides are frequently used to remove traces of water from organic solvents.
In covalent hydrides, the hydrogen atom is covalently bonded to the atom of another element. Two types of covalent hydrides: (1) with discrete molecular units (2) with complex polymeric structures.
Molecular hydrogen forms a number of hydrides with transition metals. In some of these compounds, the ratio of hydrogen atoms to metal atoms is not a constant. Such compounds are called interstitial hydrides (metallic hydrides) form when hydrogen atoms occupy empty spaces in the crystal lattice of transition metals.
Depending on the conditions, for example, the formula for titanium hydride can vary between TiH1.8 and TiH2.
Many of the interstitial hydrides have metallic properties such as electrical conductivity. Hydrogen is known to be bonded to the metal, although the exact nature of the bonding is usually unclear.
Isotopes of hydrogen include hydrogen-1 with one neutron, hydrogen-2 deuterium (D) with two neutrons, and hydrogen-3 tritium (T) with three neutrons. All of these have one proton.
D2O (deuterium oxide) resembles H2O chemically in most respects, but it is still a toxic substance. Deuterium is heavier than hydrogen-1, so its compounds react more slowly than those of the lighter isotope. Deuterium oxide is heavier, denser, and has higher melting and boiling points than H2O.
The kinetic isotope effect is seen with acid ionization constants (Ka) For example, replacing CH3COOH(aq) with CH3COOD(aq) will make the dissociation reaction three times slower for D+ than H+.
Hydrogenation is the addition of hydrogen to compounds containing multiple bonds, usually C=C double and triple bonds. The process under normal conditions is slow and the rate may be increased by using a metal catalyst and a higher temperature and pressure.
Hydrogen gas is being researched as an alternative energy source. Hydrogen gas could replace gasoline to power automobiles or be used with oxygen gas in fuel cells to generate electricity. H2 reactions are mostly void of pollutants and the final product formed in hydrogen-powered engines or fuel cells would be water: 2H2(g) + O2(g) => 2H2O(l). The challenges of hydrogen gas to be successful as alternative energy would be the affordability of production costs and the ease of storage methods.
Carbon is an essential element of living matter, but only 0.09 percent by mass of the Earth's crust. Carbon is found in the form of diamond and graphite, and natural gas, petroleum, and coal. Carbon combines with oxygen to form carbon dioxide (CO2) in the atmosphere and occurs as carbonate [CO3(2-)] in limestone and chalk rock.
Diamond and graphite are allotropes (distinct physical forms) of carbon. Although graphite is the stable form of carbon at 1 atm and 25 degrees C, the rate of spontaneous process from diamond to graphite is very slow (ΔG°= -2.87 kJ/mol).
Synthetic diamond can be produced from graphite by applying very high pressure and temperature in the laboratory.
Carbon has a unique ability to form long chains containing more than 50 carbon atoms and stable rings with five or six members. This phenomenon of linking like atoms is called catenation. Carbon's versatility allows for millions of organic compounds on Earth.
Carbides form when carbon combines with metals to form ionic compounds, such as CaC2, BeC2, SiC, Fe3C, where carbon is in the form of (C2)2- or (C)4-. These carbon ions make strong Bronsted bases and react with water to form hydroxide ions and C2H2 and CH4 respectively.
Carborundum forms when carbon forms a covalent compound with silicon (SiC): SiO2(s) + 3C(s) => SiC(s) + 2CO(g). Carborundum is almost as hard as diamond and is used industrially mainly for cutting, grinding, and polishing metals and glasses.
Cyanides are another class of carbon compounds that contain the anion group: CN-(triple bonded). Cyanides are very toxic to humans and animals because they bind to the cytochrome oxidase, an important enzyme in the metabolic process of aerobic respiration, and halt the process. Hydrogen cyanide (HCN) is even more dangerous because of its volatility and quicker reaction. Cyanide ions are also used in mining to dissolve and extract gold and silver from the ore.
Carbon monoxide (CO) and carbon dioxide (CO2) are the most important carbon oxides. Carbon monoxide is a colorless, odorless gas formed by the incomplete combustion of carbon or carbon-containing compounds: 2C(s) + O2(g) => 2CO(g) Carbon monoxide is used in metallurgical processes, it is not an acidic oxide, and it is only slightly soluble in water. Carbon dioxide is a colorless, odorless gas and is non-toxic. It is a simple asphyxiant and is used in fire extinguishers. Solid CO2 (dry ice) is used as a refrigerant.
Nitrogen is about 78 percent of air by volume. Nitrogen is an essential element of life because it is a component of proteins and nucleic acids. The N2 molecule contains a triple bond and is very stable with respect to dissociation into atomic species. Nitrogen forms a large number of compounds with hydrogen and oxygen in which the oxidation number varies from -3 to +5. Most nitrogen compounds are covalent. When heated with metals, however, nitrogen forms ionic nitrides containing the N3- ion.
The nitride ion (N3-) is a very strong Bronsted base and reacts with water to produce ammonia and hydroxide ion. Ammonia is a colorless gas with an irritating odor and is used in fertilizers. Hydrazine is another hydride of nitrogen, a colorless liquid that smells like ammonia, and a base used as a reducing agent. Hydrazine has a role in polymer synthesis and in the manufacture of pesticides.
Nitrous oxide (N2O) is a colorless gas with a pleasing odor and sweet taste. N2O resembles molecular oxygen in that it supports combustion because it decomposes when heated to form molecular nitrogen and molecular oxygen. Nitrous oxide is used in dental procedures and other minor surgery (laughing gas).
Nitric oxide (NO) is a colorless gas and is paramagnetic molecule containing one unpaired electron.
Nitrogen dioxide (NO2) is a highly toxic yellow-brown gas with a choking odor. Nitrogen dioxide is paramagnetic, and has a strong tendency to dimerize into dinitrogen tetroxide (N2O4), which is diamagnetic. Nitrogen dioxide is an acidic oxide and it reacts rapidly with cold water to form both nitrous acid (HNO2) and nitric acid (HNO3).
Nitric acid (HNO3) is one of the most important inorganic acids. Nitric acid is a liquid, but does not exist as a pure liquid because it decomposes suddenly to NO2, H2O and O2. Nitric acid is a powerful oxidizing agent and it can oxidize metals both above and below hydrogen in the activity series. Nitric acid is also used in the manufacture of fertilizers, dyes, drugs, and explosives.
Phosphorus (Group 5A element) occurs most commonly in nature as phosphate rocks, which are mostly calcium phosphate and fluoroapatite. Elemental phosphorus can be isolated by heating solid calcium phosphate (Ca3(PO4)2) with coke (solid carbon) and solid silica sand (SiO2), which produces solid CaSiO3, CO gas, and isolated solid phosphorus (P4). There are several allotropic forms of phosphorus, white (used in explosives), red (used in matches), and black phosphorus (used in electronics).
White phosphorus contains tetrahedral P4 molecules. It is insoluble in water but very soluble in carbon disulfide (CS2) and organic solvents such as chloroform (CHCl3). White phosphorus is highly toxic and bursts into flames spontaneously when exposed to air: P4(s) + 5O2(g) => P4O10 (s).
When heated in the absence of air, white phosphorus is slowly converted to red phosphorus at about 300 degrees C: P4 (white phosphorus) => P4 (red phosphorus). Red phosphorus has a polymeric structure and is more stable and less volatile than white phosphorus.
Phosphine (PH3) is the most important hydride of phosphorus. PH3 is a colorless, very poisonous gas formed by heating white phosphorus in concentrated sodium hydroxide. Phosphine is moderately soluble in water and more soluble in carbon disulfide and organic solvents. Phosphine is a strong reducing agent and it reduces many metal salts to the corresponding metals. Phosphine gas burns in air: PH3(g) + 2O2(g) => H3PO4(s).
Phosphorus forms binary compounds with halogens-namely, the trihalides (PX3) and the pentahalides (PX5). The two imp0rtant oxides of phosphorus are tetraphosphorus hexoxide (P4O6) and tetraphosphorus decoxide (P4O10). The oxides are isolated by burning white phosphorus in limited and excess amounts of oxygen gas, respectively.
P4(s) + 3O2(g) => P4O6(s)
P4(s) + 5O2(g) => P4O10(s)
Both oxides are converted to acids in water. The compound P4O10 is a white flocculent powder that has a great affinity for water: P4O6(s) + 6H2O(l) => 4H3PO4(aq). For this reason, P4O10 is often used for drying gases and for removing water from solvents.
There are many oxoacids containing phosphorus: Phosphorus acid (H3PO3), Hypophosphorous acid (H3PO2), Phosphoric acid (H3PO4), and Triphosphoric acid (H5P3O10).
Phosphoric acid and phosphates have many commercial applications in detergents, fertilizers, flame retardants, and toothpastes, and as buffers in carbonated beverages.
Phosphorus is an element that is essential for life. Phosphorus is only about 1 percent by mass of the human body. However, the human skeleton is 23 percent mineral matter, the phosphorus content of which (calcium phosphate), is 20 percent. Phosphates are also important components of the genetic material in DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Oxygen is the most abundant element in the Earth's crust (46 percent of mass). In addition, the atmosphere is about 21 percent molecular oxygen by volume as a diatomic molecule (O2). Oxygen is a building block of almost all biomolecules (25 percent of all biomatter). Molecular oxygen is the essential oxidant in the metabolic breakdown of food molecules.
Oxygen (O2) has one other allotrope, (O3, ozone) which is less stable than O2. The O2 molecule is paramagnetic with two unpaired electrons. Molecular oxygen is a strong oxidizing agent and is one of the most widely used industrial chemicals. Oxygen forms three types of oxides: oxide (O2-), peroxide [(O2)2-], and superoxide (O2-). The ions are all strong Bronsted bases and react with water:
Oxide: O2-(aq) + H2O(l) => 2OH-(aq) (hydrolysis reaction)
Peroxide: 2(O2)2-(aq) + 2H2O(l) => O2(g) + 4OH- (redox reaction)
Superoxide: 4(O2)-(aq) + 2H2O(l) => 3O2(g) + 4OH-(aq) (redox reaction)
The nature of bonding in oxides changes across any period in the periodic table, from basic oxides (Na2O, CaO, MgO, FeO), to amphoteric (acid or base, Al2O3, ZnO), to acidic oxides (SO2, SO3, CO2, N2O5, N2O3, P4O10). The basicity of the oxides increases as we move down a particular group of the Periodic Table, and acidity decreases as we move down a group.
Hydrogen Peroxide (H2O2) is a colorless viscous (thick) liquid chemical used for cleaning, disinfecting, and bleaching. Hydrogen peroxide readily decomposes when heated or exposed to sunlight into liquid water and O2 gas. 2H2O2(l) => 2H2O(l) + O2(g) ΔH°=-196.4 kJ/mol. This is a disproportionation reaction=a redox reaction where a single element in one reactant simultaneously undergoes both oxidation (loses electrons) and reduction (gains electrons) to form two different products because the element is an intermediate oxidation state and can both increase and decrease its oxidation number. The oxidation number of oxygen changes from 1- to -2 and 0.
Dilute hydrogen peroxide solutions (3% by mass) are used as mild antiseptics and more concentrated H2O2 solutions are used as bleaching agents. The high heat of decomposition also makes hydrogen peroxide a suitable component in rocket fuel.
Ozone is a toxic, light-blue gas and its strong odor is noticeable around electrical discharges and after lightning strikes. Ozone is less stable than molecular oxygen. The ozone molecule has a bent structure with three oxygen atoms, one at each end and one at the bend, two atoms of which are double bonded and the other oxygen is single bonded. Ozone is used to purify water, deodorize air and sewage gases, and to bleach waxes, oils, and textiles. Ozone oxidizes all common metals except gold and platinum. 3O2 =>2O3 (g) ΔG∘ = 326.8 kJ/mol is the change in Gibbs Free Energy needed to convert O2 to O3.
Sulfur occurs in nature in elemental form and the largest known reserves are found in sedimentary deposits, including gypsum and sulfide minerals including pyrite, and natural gas as H2S and SO2.
Allotropes of sulfur are rhombic and monoclinic forms. Rhombic sulfur is thermodynamically the most stable form and it has an atomic ring structure (S8) that is wrinkled in shape. Sulfur is yellow, tasteless, and odorless solid insoluble in water but soluble in carbon disulfide. When heated, it is slowly converted to monoclinic sulfur, which also consists of S8 units. When sulfur is heated above 150 degrees, the rings break up. Sulfur has several oxidation numbers, from -2, 0, +1, +2, +4, +6.
Hydrogen sulfide (H2S) is a colorless gas that smells like rotten eggs and it is highly toxic because it attacks the respiratory system in humans and animals. Sulfur oxides are sulfur dioxide (SO2) and sulfur trioxide (SO3). Sulfur dioxide has a strong smell and is a colorless gas that is very toxic. SO2 can be oxidized to sulfur trioxide. 2SO2(g) + O2(g) => 2SO3(g).
Sulfur trioxide dissolves in water to form sulfuric acid: SO3(g) + H2O(l)=> H2SO4(g). Sulfuric acid is one of the most important industrial chemicals. Sulfuric acid is a diprotic acid, colorless, thick, viscous fluid. Laboratory sulfuric acid is 98 percent H2SO4. Concentrated sulfuric acid oxidizes metals.
Carbon disulfide (CS2) is a two-double bond structure molecule, colorless, flammable liquid formed by heating carbon and sulfur to a high temperature. C(s) + 2S(l) =>CS2(l).
Sulfur hexafluoride (SF6) is a nontoxic, colorless gas, and the most inert of all sulfur compounds.
Halogens: Fluorine, chlorine, bromine, and iodine are reactive nonmetals. Fluorine is the most reactive of all the halogens. Hydrogen fluoride (HF) has a high boiling point of 19.5 degrees C as a result of strong intermolecular hydrogen bonding, but other hydrogen halides have lower boiling points. Hydrofluoric acid (HF dissolved in water) is a weak acid, but all other hydrohalic acids (HCl, HBr, and HI) are strong acids. Fluorine reacts with cold sodium hydroxide solution to produce oxygen difluoride. Silver fluoride (AgF) is soluble, but all other silver halides are insoluble.
Fluorine and chlorine are strong oxidizing agents and must be prepared by electrolysis. The hydrogen halides can be formed by the direct combination of elements: H2(g) + X2(g) => 2HX(g), where X represents a halogen and the reactions can occur explosively.
In the laboratory, hydrogen fluoride and hydrogen chloride can be prepared by combining the metal halide with concentrated sulfuric acid:
CaF2(s) + H2SO4(aq) => 2HF(g) + CaSO4(s)
2NaCl(s) + H2SO4(aq) =>2HCl(g) + Na2SO4(aq)
HF is very highly reactive and its attacks silica, so it is used for etching glass.
Aqueous solutions of hydrogen halides are acidic and the strength of the acids increases from: HF << HCl< HBr< HI.
The halogens also form a series of oxoacids with the general formulas: HXO (hypohalous acid), HXO2 (halous acid), HXO3 (halic acid), HXO4 (perhalic acid), where X represents a halogen element.
NaF is used in drinking water to reduce dental caries (cavities). UF6 is used to separate U-235 and U-238 isotopes. Fluorine F is used to produce the polymer Teflon. Chlorine Cl works in the human body as the principle anion in intracellular and extracellular fluids. Chlorine is also used to purify water. Silver bromide AgBr is used in photographic films. Iodine is used in medicine as an antiseptic. Silver Iodide AgI is used in cloud seeding to induce rainfall.