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Lead(II) oxide
Encyclopedia
Lead oxide is the inorganic compound
with the formula
Pb
O
. Lead(II) oxide occurs in two polymorph
s, red, having a tetragonal crystal structure
and yellow, having an orthorhombic crystal structure
. Both forms occur naturally as rare minerals: the red form is known as litharge
and the yellow form is known as massicot
.
Thermal decomposition of lead(II) nitrate or lead carbonate also results in the PbO formation:
As determined by X-ray crystallography
, the compound features pyramidal four-coordinate Pb center. The pyramidal nature indicates the presence of a stereo-chemically active lone pair
of electrons.
:
PbO(red) → PbO(yellow) ΔH = 1.6 kJ/mol
PbO is amphoteric, which means that it reacts with both acids and with bases. With acids, it forms salts of Pb2+ via the intermediacy of oxo cluster
s such as [Pb6O(OH)6]4+. With strong base, PbO dissolves to form plumbite
(II) salts:
PbO + H2O + OH- → [Pb(OH)3]-
into metallic lead. The consumption of lead, and hence the processing of PbO, correlates with the number of automobiles because it remains the key component of automotive lead-acid batteries.
PbO is used extensively in manufacturing of lead glass
es and ceramic glaze
s as well as in fine dinnerware. For such applications, the PbO is converted in situ to lead silicate, which is less toxic. Other less dominating applications include the vulcanization
of rubber and the production of certain pigments and paints. PbO is used in cathode ray tube
glass to block X-ray
emission, but mainly in the neck and funnel because it can cause discoloration when used in the faceplate. Strontium oxide
is preferred for the faceplate.
, and was also once used to seal glass panels in window frames. It is a component of lead paint
s.
PbO is used in certain condensation reaction
s in organic synthesis
.
Lead oxide may be fatal if swallowed or inhaled. It causes irritation to skin, eyes, and respiratory tract. It affects gum tissue, central nervous system, kidneys, blood, and reproductive system. It can bioaccumulate in plants and in mammals.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Pb
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
O
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
. Lead(II) oxide occurs in two polymorph
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
s, red, having a tetragonal crystal structure
Tetragonal crystal system
In crystallography, the tetragonal crystal system is one of the 7 lattice point groups. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base and height .There are two tetragonal Bravais...
and yellow, having an orthorhombic crystal structure
Orthorhombic crystal system
In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...
. Both forms occur naturally as rare minerals: the red form is known as litharge
Litharge
Litharge is one of the natural mineral forms of lead oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coatings and encrustations with internal tetragonal crystal structure. It is dimorphous with the orthorhombic form massicot...
and the yellow form is known as massicot
Massicot
Massicot is one of the natural mineral forms of lead oxide, PbO. Massicot is the orthorhombic dimorph of the tetragonal form of lead oxide, litharge. It forms soft yellow to reddish-yellow, earthy, scaley masses which are very dense, with a specific gravity of 9.64.It was first described in 1841...
.
Preparation and structure
PbO may be prepared by heating lead metal in air at approx. 600 °C. At this temperature it is also the end product of oxidation of other lead oxides in air:- PbO2 –(293 °C)→ Pb12O19 –(351 °C)→ Pb12O17 –(375 °C)→ Pb3O4 –(605 °C)→ PbO
Thermal decomposition of lead(II) nitrate or lead carbonate also results in the PbO formation:
- 2 Pb(NO3)2 → 2 PbO + 4 NO2 + O2
- PbCO3 → PbO + CO2
As determined by X-ray crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
, the compound features pyramidal four-coordinate Pb center. The pyramidal nature indicates the presence of a stereo-chemically active lone pair
Lone pair
In chemistry, a lone pair is a valence electron pair without bonding or sharing with other atoms. They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons...
of electrons.
Reactions
The red and yellow forms of this material are related by a small change in enthalpyEnthalpy
Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...
:
PbO(red) → PbO(yellow) ΔH = 1.6 kJ/mol
PbO is amphoteric, which means that it reacts with both acids and with bases. With acids, it forms salts of Pb2+ via the intermediacy of oxo cluster
Cluster chemistry
In chemistry, a cluster is an ensemble of bound atoms intermediate in size between a molecule and a bulk solid. Clusters exist of diverse stoichiometries and nuclearities. For example, carbon and boron atoms form fullerene and borane clusters, respectively. Transition metals and main group...
s such as [Pb6O(OH)6]4+. With strong base, PbO dissolves to form plumbite
Plumbite
In chemistry, a plumbite is a salt having one of several lead-containing oxoanions in which lead is in the oxidation state +2. The term plumbite may also refer to the oxoanion itself...
(II) salts:
PbO + H2O + OH- → [Pb(OH)3]-
Applications
PbO is produced on a large scale as an intermediate in the conversion of lead ores, mainly galenaGalena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
into metallic lead. The consumption of lead, and hence the processing of PbO, correlates with the number of automobiles because it remains the key component of automotive lead-acid batteries.
PbO is used extensively in manufacturing of lead glass
Lead glass
Lead glass is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40 weight% lead oxide , while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO...
es and ceramic glaze
Ceramic glaze
Glaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
s as well as in fine dinnerware. For such applications, the PbO is converted in situ to lead silicate, which is less toxic. Other less dominating applications include the vulcanization
Vulcanization
Vulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives." These additives modify the polymer by forming crosslinks between individual polymer chains. Vulcanized material is...
of rubber and the production of certain pigments and paints. PbO is used in cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
glass to block X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
emission, but mainly in the neck and funnel because it can cause discoloration when used in the faceplate. Strontium oxide
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
is preferred for the faceplate.
Niche or declining uses
A mixture of PbO with glycerine sets to a hard, waterproof cement that has been used to join the flat glass sides and bottoms of aquariaAquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
, and was also once used to seal glass panels in window frames. It is a component of lead paint
Lead paint
Lead paint or lead-based paint is paint containing lead, a heavy metal, that is used as pigment, with lead chromate and lead carbonate being the most common. Lead is also added to paint to speed drying, increase durability, retain a fresh appearance, and resist moisture that causes corrosion...
s.
PbO is used in certain condensation reaction
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
s in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
.
Health issues