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Chapter 5
Molecular Compounds

05-00-01UN

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Title
Structure of water
Caption
Two hydrogen atoms + one oxygen atom combine to give one water molecule.
Notes
covalent bonds are bonds formed by sharing electrons between atoms. A molecule is a gorup of atoms held together by covalent bonds.
Keywords
covalent bond, molcule
05-01

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Title
Covalent bonding
Caption
A covalent bond is the result of attractive and repulsive forces between atoms.
Notes
Nucleus-electron attractions are greater than the nucleu-nucleus and electron-electron repulsions. The net attractive force holds the atoms together.
Keywords
covalent bond, molecule
05-01-02UN

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Title
Formation of a hydrogen molecule
Caption
Two hydrogen atoms share an electron pair to make a hydrogen molecule.
Notes
The covalent bond in hydrogen can be imagined as an overlap between two spherical orbitals in hydrogen atoms. The electron density in the resulting molecule is greatest between the two nuclei.
Keywords
covalent bond, molecule
05-02

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Title
potential energy diagram for bond formation
Caption
A graph of potential energy versus internuclear distance for hydrogen.
Notes
If the hydrogen atoms are too far apart, attractions are weak and no bonding occurs. If the atoms are too close, strong repulsions occur. The minimum potential energy occurs at an optimal distance between the nuclei. This distance is the bond length.
Keywords
potential energy, covalent bond, molecule, bond length
05-02-01

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Title
orbital overlap in chlorine
Caption
In chlorine gas, (Cl2), overlap of 3p orbitals produces a covalent bond.
Notes
In chlorine gas (Cl2), 3p electrons are involved in covalent bond formation. The orbital overlap occurs between two 3p orbitals that each contain just one electron. The shared electron pair bonds the chlorine atoms together.
Keywords
covalent bond, molecule, orbital overlap
05-03

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Title
diatomic elements
Caption
Diatomic elements in the periodic table
Notes
Seven elemental substances occur as diatomic molecules. These are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.
Keywords
molecules, diatomic, elements, periodic table
05-03-01UN

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Title
molecular comounds
Caption
water, ammonia, and methane are three important molecular compounds.
Notes
Each of these compounds forms covalent bonds in such a way as to provide every atom in the molecule with a noble gas electron configuration.
Keywords
covalent bond, molecule, molecular comopund, octet rule
05-04

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Title
numbers of bonds formed by main group elements
Caption
For P, S, Cl, and other elements in the third period and below, the number of covalent bonds may vary, as indicated by the numbers shown in parentheses and explained in the text.
Notes
The bonding behavior of these atoms is related to the octet rule. By forming the number of bonds indicated, atoms are able to attain a noble gas configuration.
Keywords
covalent bonds, octet rule, valence electrons
05-04-01UN

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Title
Exceptions to the octet rule
Caption
The octet rule is a useful guide, but exceptions do exist.
Notes
Compounds may form with either less than or more than an octet.
Keywords
octet rule, electron, covalent bond
05-04-04UN

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Title
multiple bonds
Caption
Carbon and two oxygen atoms can gain noble gas electron configurations by forming double bonds. Two nitrogen atoms can gain noble gas configurations by forming a triple bond.
Notes
Keywords
single bond, double bond, triple bond, multiple bonds, octet rule
05-04-05UN

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Title
Bonding in ethylene
Caption
The carbon atoms in ethylene are bound by a double bond.
Notes
Keywords
covalent bond, octet rule, multiple bond, double bond
05-04-06UN

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Title
bonding in acetylene
Caption
The two carbons in acetylene are bound by a triple bond.
Notes
Keywords
covalent bond, multiple bond, triple bond, octet rule
05-04-12UN

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Title
coordinate covalent bonds
Caption
Typical covalent bonds involve two electrons from different atoms. Coordinate covalent bonds form when both shared electrons come from one atom.
Notes
Keywords
coordinate covalent bond
05-05UN

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Title
molecular vs. ionnic compounds
Caption
The distinction between molecular and ionic compounds.
Notes
In molecular compounds, the smallest particle is a molecule. In ionic compounds, the smallest particle is an ion.
Keywords
ionic compounds, molecular compounds, ionic bond, covalent bond, molecule
05-05-01UN

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Title
bonding patterns in some common elements
Caption
Carbon, nitrogen, oxygen, halogen, and hydrogen atoms usually maintain consistent bonding patterns.
Notes
Keywords
bonding, octet rule
05-05-02UN

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Title
structures of ethane and acetaldehyde
Caption
Lewis structures for ethane and acetaldehyde
Notes
Lewis structures for ethane and acetaldehyde show how the octet rule can be used to explain the structures of many-atom molecules.
Keywords
Lewis structure, octet rule, covalent bond, molecule
05-05-03UN

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Title
Space-filling and ball-and-stick models
Caption
Space-filling and ball-and-stick models of several compounds are shown.
Notes
Space-filling models are perhaps more realistic pictures of compounds, but ball-and-stick models allow visualization of bonds as well as atoms.
Keywords
model, space-filling, ball-and-stick
05-05-04UN

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Title
Ball-and-stick model of HCN
Caption
A ball-and-stick model of HCN
Notes
A triple bond is necessary between the carbon and nitrogen in this compound. A pair of nonbonding electrons sits on the nitrogen atom.
Keywords
Lewis structure, ball-and-stick model, multiple bond, triple bond
05-05-05UN

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Title
Ball-and-stick model of vinyl chloride
Caption
A ball and stick and Lewis structure for the compound vinyl chloride.
Notes
Vinyl chloride contains two carbons bound by a double bond. The double bond is necessary to give the carbons filled octets. Put another way, it is necessary to give carbon its usual number of bonds--four.
Keywords
Lewis structure, ball-and-stick model, multiple bond, double bond
05-05-07UN

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Title
Ball-and-stick model for methyl methacrylate
Caption
Methylmethacrylate is a compound used to prepare Lucite plastic. What is the formula for this compound? Does this compound contain any multiple bonds?
Notes
Keywords
ball-and-stick model, Lewis structure, molecular formula, multiple bond, lone pair
05-05-14T5.1

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Title
Table of molecular geometry around atoms with 2, 3, and 4 charge clouds
Caption
Molecular geometry around atoms with 2, 3, and 4 charge clouds
Notes
Molecular geometry is a consequence of the number of charge clouds and the number of lone pairs around an atom.
Keywords
molecular geometry, lone pair, bond angle, shape
05-05-15UN

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Title
Structures of HCN and CO2
Caption
Both HCN and CO2 are linear molecules with a bond angle of 180 degrees.
Notes
The presence of two charge clouds and no lone pairs around the central carbon atom in each of these molecules means the molecules with have a linear shape.
Keywords
bond angle, Lewis structure, molecular shape, charge cloud, linear
05-05-16UN

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Title
Molecular shape of formaldehyde
Caption
Formaldehyde is a planar triangular molecule. Bond angles in the plane are about 120 degrees.
Notes
The carbon in formaldehyde is surrounded by three charge clouds--3 bonds and no lone pairs of electrons. As a result, the shape of this molecule is planar triangular.
Keywords
planar triangular, charge clouds, molecular shape, lone pair
05-05-17UN

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Title
Molecular shape of SO2
Caption
SO2 is a bent molecule, with bond angles of approximately 120 degrees.
Notes
The sulfur in SO2 is surrounded by 3 charge clouds. Two bonds and one lone pair surround this atom. As a result, the shape of the molecule is bent, and the bond angle is about 120 degrees.
Keywords
bond angle, bent, molecular shape, charge clouds, lone pair
05-06a-c

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Title
Tetrahedral geometry
Caption
The tetrahedral geometry of an atom surrounded by four charge clouds.
Notes
The atom is in the center of the regular tetrahedron, and the four charge clouds point toward the corners. The bond angle between the center and any two corners in 109.5 degrees.
Keywords
molecular shape, tetrahedron, bond angle
05-06-01UN

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Title
Molecular shapes based on the tetrahedron
Caption
Many molecules have shapes based on the tetrahedron. A central atom connected to others by four bonds produces a tetrahedral structure. When lone pairs are included in the overall structure, pyramidal or bent molecules are the result.
Notes
Bond angles deviate a little from the regular tetrahedron bond angle of 109.5 in molecules with lone pairs. The lone pairs compress the other bonds slightly--resulting in bond angles of closer to 107 degrees in ammonia and 104.5 degrees in water.
Keywords
molecular shape, tetrahedron, lone pair, pyramidal, bent
05-06-02UN

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Title
The molecular shape of ethylene
Caption
Ethylene is planar, with bond angles of 120 degrees around both carbons.
Notes
The shapes of larger molecules are related to the geometry around individual atoms in the molecules. Each carbon in ethylene is surrounded by three charge clouds and no lone pairs, producing a planar triangular arrangement. When put together, the entire molecule is planar.
Keywords
molecular shape, planar, planar triangular, bond angle
05-06-03UN

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Title
Molecular shape for ethane
Caption
Ethane has two tetrahedral carbon atoms.
Notes
The molecular shape that results is a consequence of the arrangement of bonds around these two carbons. Each carbon is surrounded by four bonds, with bond angles of 109.5 degrees.
Keywords
molecular shape, bond angle, tetrahedron
05-06-04UN

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Title
Molecular shape of hydronium ion
Caption
What would you expect to be the molecular shape of the hydronium ion, H3O+?
Notes
The Lewis structure for the hydronium ion shows four charge clouds around the central oxygen atom. Three are bonds and the fourth is a lone pair. Therefore the shape is pyramidal. Bond angles are about 109.5 degrees.
Keywords
molecular shape, bond angle, pyramidal, ion
05-06-05UN

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Title
The molecular geometry for acetaldehyde
Caption
Predict the molecular geometry of acetaldehyde.
Notes
One carbon on acetaldehyde is connected to four other atoms through bonds, resulting in a tetrahedral arrangement. The other carbon has only three bonds, so the arrangement around it is planar triangular. Therefore the overall structure is as shown.
Keywords
molecular shape, tetrahedron, planar triangular, bond angle
05-06-06UN

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Title
Molecular shape for the amino acid methionine
Caption
Describe the molecular geometry for methionine, including the shapes around each atom marked with an arrow.
Notes
For each atom considered, count bonds and lone pairs of electrons. Use the table on page 113 to determine the shape and bond angles around those atoms.
Keywords
molecular shape, bond angle, tetrahedron, planar tirangular, bent, lone pair
05-06-07UN

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Title
Polymers
Caption
Polymers can be composed of repeated identical units.
Notes
Keywords
polymer
05-06-09UN

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Title
Plar bonds
Caption
Polar covalent bonds are bonds in which the electrons are attracted more strongly by one atom than be the other.
Notes
In a polar molecule, there is no overall charge but the unequal distribution of electrons results in what are called partial charges. The partial charges are represesnted with a Greek lower case delta followed by the nature of the charge written at each end of the polar bond. The electron-rich end of the bond is partially negative while the electron-poor end is partially positive.
Keywords
polar, polar covalent bond, partial charge, electronegativity
05-07

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Title
Electronegativities and the periodic table
Caption
Electronegativities of main group elements and several transition metal elements. Reactive nonmetals at the top right of th eperiodic talbe are most electronegative, and metals at the lower left are least electronegative. The noble gasees are not assigned values.
Notes
Keywords
electronegativity, polar, polar covalent bond
05-07-01UN

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Title
Quantitative determination of polarity
Caption
Calculating the difference in electronegativities between two bonding atoms allows a quantitative assessment of the degree of polarity.
Notes
If the electronegativity difference is small, the bond is relatively nonpolar. If the electronegativity difference is large, the bond is very polar. At the extreme, bonds are considered ionic.
Keywords
electronegativity, polar, polar covalent bond, nonpolar, ionic
05-07-02UN

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Title
Calculated differences in electronegativity
Caption
Electronegativity differences in several bonds are shown.
Notes
The bond between carbon and fluorine is considered highly polar, while the bonds between sodium and chlorine and rubidium and fluorine are considered ionic.
Keywords
polar, polar covalent bond, ionic, electronegativity
05-07-03UN

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Title
Electrostatic potential maps for water and chloromethane
Caption
Molecular polarity depends on both the polarity of bonds and molecular shape.
Notes
In water and chloromethane, polar bonds combine with a bent shape to produce a molecule that is polar. Electrostatic potential maps clearly show the abundance of electron density at one end of each of these molecules.
Keywords
polar, electrostatic potential map, electonegativity
05-07-04UN

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Title
Electrostatic density maps for carbon dioxide and carbon tetrachloride
Caption
In carbon dioxide and carbon tetrachloride, symmetrical molecular shapes cause molecules with polar bonds to be nonpolar. Electrostatic density maps show the even distribution of electron density around central atoms in each case.
Notes
Keywords
electrostatic potential map, polar, electronegativity
05-07-05UN

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Title
Is HCN a polar molecule?
Caption
HCN is polar. The carbon to nitrogen bond is polarized, with excess electron density (a partial negative end to the bond) around the nitrogen. The electrostatic density map shows this.
Notes
Keywords
electrostatic potential map, polar, electronegativity
05-07-06UN

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Title
Is vinyl chloride a polar molecule?
Caption
The hydrogen to carbon and carbon to carbon bonds in vinyl chloride are nonpolar. However, the carbon to chlorine bond is polar, with an excess of electron density around the chlorine. This molecule is therefore polar, with a partially-negative end around the chlorine atom.
Notes
Keywords
electrostatic potential map, electronegativity, partial charge, polar
05-07-07UN

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Title
Explain the polarity of methyllithium
Caption
Look at the electrostatic potential map and consider electronegativity values for this compound.
Notes
Keywords
electrostatic potential map, polar, electronegativity
05-07-08UN

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Title
naming binary compounds
Caption
The names of binary compounds are assigned in two steps, using prefixes to indicate the number of atoms of each element combined.
Notes
Step one is to name the first element in the formula. Step two is to namethe second element in the formula, replacing the regular ending with an "-ide" ending, and using a prefix as needed. For example, the first model above represents titanium chloride.
Keywords
binary compound, naming, prefix
05-07-09UN

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Title
Use of prefixes in naming binary compounds
Caption
In the examples given, prefixes are used to show the number of atoms in these binary compounds.
Notes
"Mono" is generally not used in names, unless it is important to distinguish the compound from other very similar forms with "di" or "tri" prefixes. An example of the use of "mono" is in carbon monoxide. If a prefix is not used, "mono" is assumed, as in boron tribromide, which contains one boron.
Keywords
naming, binary compound
05-07-11UN

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Title
Ionic and covalent compounds
Caption
Which of the drawings is more likely to represent an ionic compound and which a covalent compound?
Notes
Since covalent compounds form discrete molecules, drawing (b) is the better representation of this type of compound. Ionic compounds are aggregates of oppositely charged ions. Drawing (a) therefore is the better representation of this type of compound.
Keywords
ionic compound, covalent compound, ionic bond, covalent bond, molecule
05-07-14UN

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Title
molecular geometry
Caption
Three of the following molecular models have a tetrahedral central atom, and one does not. Which is the odd one?
Notes
Drawing (c) contains a central atom that is not linked to other atoms tetrahedrally,
Keywords
molecular geometry, tetrahedral
05-07-15UN

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Title
ball and stick model of acetaminophen
Caption
The ball and stick model shown represents acetaminophen, the active ingredient in the drug Tylenol. Determine the molecular formula for this compound, and assess the bonds in it. Which are multiple bonds? What is the geometry around each carbon and nitrogen?
Notes
Keywords
molecular geometry, tetrahedral, trigonal planar, bonds, covalent compound
05-07-17UN

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Title
Ball and stick model of thalidomide
Caption
The ball and stick model shown represents thalidomide, a drug that caused terrible birth defects when taken by expectant mothers but is now approved to use against leprosy. Determine the molecular formula for this compound, and assess the bonds in it. Which are multiple bonds? What is the geometry around each carbon and nitrogen?
Notes
Keywords
molecular geometry, tetrahedral, trigonal planar, bonds, covalent compound
05-07-18UN

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Title
Electrostatic potential map for acetamide
Caption
Show the position of any electron lone pairs, and indiecate the electron-rich and electron-poor regions in acetamide.
Notes
Keywords
electrostatic potential map, electronegativity, lone pair
05-07-20UN

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Title
Lewis structure for thionyl chloride
Caption
Thionyl chloride has the structure shown. Which bond in thionyl chloride is a coordinate covalent bond?
Notes
The sulfur to oxygen bond.
Keywords
coordinate covalent bond
05-07-12UN

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Title
Sphere representations of molecules
Caption
If yellow spheres represent sulfur atoms and red spheres represent oxygen atoms, which of the following drawings depicts a collection of sulfur dioxide molecules?
Notes
Each molecule of sulfur dioxide contains one sulfur (yellow sphere) and two oxygens (red spheres). Drawing (a) shows molecules with this makeup.
Keywords
molecule, covalent compounds, sphere representations

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