Questions and Answers
A structural formula shows the arrangement of the atoms in a molecule.
True
The central atom in a molecule is the one with the highest electron affinity.
False
In molecules, hydrogen is always a terminal atom.
True
The number of bonding pairs in a molecule is equal to the number of electrons.
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To find the total number of electrons available for bonding in a positive ion, you should add the ion charge to the total number of valence electrons of the atoms present.
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The electrons in a coordinate covalent bond are donated by both bonded atoms.
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Resonance occurs when more than one valid Lewis structure can be written for a molecule.
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Nitrate is an example of an ion that forms resonance structures.
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The carbon dioxide molecule contains two double bonds.
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All electrons in an atom are available for bonding.
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In the sulfate ion (SO4 2-), 32 electrons are available for bonding.
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When carbon and oxygen bond, the molecule contains ten pairs of bonding electrons.
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Identify the molecule with an odd number of valence electrons.
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Identify the molecule with fewer than 8 electrons around an atom.
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Identify the molecule with more than 8 electrons around the central atom.
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Identify the molecule that has more than one valid Lewis structure.
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The VSEPR model is used mainly to determine what?
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What is the bond angle?
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What is the basis of the VSEPR model?
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What is the shape of a molecule whose central atom has four pairs of bonding electrons?
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What is the shape of a molecule that has two covalent single bonds and no lone pairs on the central atom?
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What is the shape of a molecule that has three single covalent bonds and one lone pair on the central atom?
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The formation of new orbitals from a combination or rearrangement of valence electrons is called __.
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The orbitals that are produced through hybridization are __ to one another.
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An example of an element that commonly undergoes hybridization is __.
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When carbon combines three p orbitals and its one s orbital, the orbitals that result are called __.
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An example of a molecule that has sp3 is __.
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What is the meaning of the term electronegativity?
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Which element has the highest electronegativity? What is the numerical value? What are the name and group number of the chemical family that has the highest overall electronegativities?
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Which element has the lowest electronegativity? What is the numerical value? What are the name and group number of the chemical family that has the lowest overall electronegativities?
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What general trend in electronegativity do you note going down a group? Across a period?
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How are the electronegativity values used to determine the type of bond that exists between two atoms?
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Ionic compounds are usually soluble in polar substances.
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In a covalent molecular compound, the attraction between molecules tends to be strong.
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Unequal sharing of electrons between two bonded atoms always indicates what?
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When electronegativities of two bonded atoms differ greatly, the bond is what?
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What is the electronegativity difference that usually is the dividing line between covalent and ionic bonds?
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The symbol delta is placed next to what?
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A nonpolar covalent bond is one in which?
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Molecules containing only polar covalent bonds?
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What factor other than electronegativity determines whether a molecule as a whole is polar or not?
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What correctly describes the compound water H2O?
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What correctly describes the compound carbon tetrachloride, CCl4?
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A molecule of ammonia, NH3, is?
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Study Notes
Structural Formulas and Bonding
- A structural formula illustrates the arrangement of atoms within a molecule.
- In a molecule, hydrogen atoms are always positioned as terminal atoms.
- The number of bonding pairs does not equal the total number of electrons in a molecule.
- The electrons in a coordinate covalent bond are only donated by one atom, not both.
Resonance and Molecular Structures
- Resonance occurs when multiple valid Lewis structures can be created for a single molecule.
- Nitrate (NO3-) is an example of an ion that can have resonance structures.
- Carbon dioxide (CO2) contains two double bonds, contributing to its linear structure.
Bonding Electrons and Ions
- In the sulfate ion (SO4 2-), a total of 32 electrons are available for bonding.
- Electrons in an atom are not all available for bonding due to filled electron shells.
Molecular Geometry and VSEPR Theory
- The VSEPR model is utilized to determine the shapes of molecules based on electron pair repulsion.
- Bond angles are measured between two terminal atoms and the central atom within a molecule.
- Molecules can exhibit various shapes:
- Tetrahedral shape occurs with four pairs of bonding electrons.
- Linear shape is formed with two covalent single bonds without lone pairs.
- Trigonal pyramidal shape has three single covalent bonds and one lone pair.
Hybridization
- Hybridization refers to the formation of new orbitals from combined valence electrons.
- Hybrid orbitals generated are identical to one another, such as in carbon.
- Carbon commonly undergoes hybridization, forming sp3 orbitals when combining three p orbitals with one s orbital.
- Methane (CH4) is an example of a molecule displaying sp3 hybridization.
Electronegativity
- Electronegativity measures an atom's ability to attract electrons in a bond.
- Fluorine holds the highest electronegativity value at 3.98 among all elements, classified under halogens in group 7A.
- Francium has the lowest electronegativity at 0.7, belonging to alkali metals in group 1A.
- Electronegativity decreases down a group and increases across a period.
Bond Types and Properties
- The difference in electronegativities indicates bond type: a difference of 1.7 or more typically indicates an ionic bond.
- Polar covalent bonds result from unequal electron sharing between bonded atoms.
- A nonpolar covalent bond involves equal electron sharing between atoms.
- The delta symbol (δ) indicates the less electronegative atom in a polar covalent bond.
Molecular Polarity
- Molecules with only polar covalent bonds may or may not exhibit overall polarity based on their geometric arrangement.
- Water (H2O) is considered a polar molecule with polar covalent bonds and unique geometry (bent).
- Carbon tetrachloride (CCl4) is nonpolar overall, despite containing polar covalent bonds.
- Ammonia (NH3) is polar because significant electronegativity differences result in a trigonal pyramidal shape.
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Test your understanding of key concepts from Chemistry Chapter 9 with these flashcards. Each card explores important definitions and statements regarding molecular structures and bonding. Perfect for quick review and reinforcement of your chemistry knowledge!
