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Questions and Answers
What is a chemical bond?
What is a chemical bond?
A mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together.
Identify and define the three major types of chemical bonding.
Identify and define the three major types of chemical bonding.
- Ionic
- Polar Covalent
- Non-Polar Covalent
- All of the above (correct)
What is the relationship between electronegativity and the ionic character of a chemical bond?
What is the relationship between electronegativity and the ionic character of a chemical bond?
The higher the difference in electronegativity values between atoms, the greater the ionic character of the bond.
What is the meaning of the term polar, as applied to chemical bonding?
What is the meaning of the term polar, as applied to chemical bonding?
Distinguish between polar-covalent and nonpolar-covalent bonds.
Distinguish between polar-covalent and nonpolar-covalent bonds.
In general, what determines whether atoms will form chemical bonds?
In general, what determines whether atoms will form chemical bonds?
What is a molecule?
What is a molecule?
What determines bond length?
What determines bond length?
In general, how are bond energies and bond lengths related?
In general, how are bond energies and bond lengths related?
Describe the general location of the electrons in a covalent bond.
Describe the general location of the electrons in a covalent bond.
What is meant by an unshared or lone pair of electrons?
What is meant by an unshared or lone pair of electrons?
Describe the octet rule in terms of noble-gas configurations.
Describe the octet rule in terms of noble-gas configurations.
When drawing Lewis structures, which atom is usually the central atom?
When drawing Lewis structures, which atom is usually the central atom?
Distinguish between single, double, and triple covalent bonds.
Distinguish between single, double, and triple covalent bonds.
In writing Lewis structures, how is the need for multiple bonds determined?
In writing Lewis structures, how is the need for multiple bonds determined?
What is an ionic compound?
What is an ionic compound?
In what form do most ionic compounds occur?
In what form do most ionic compounds occur?
What is a formula unit?
What is a formula unit?
What are the components of one formula unit of CaF2?
What are the components of one formula unit of CaF2?
What is lattice energy?
What is lattice energy?
In general, what is the relationship between lattice energy and the strength of ionic bonding?
In general, what is the relationship between lattice energy and the strength of ionic bonding?
In general, how do ionic and molecular compounds compare in terms of melting points?
In general, how do ionic and molecular compounds compare in terms of melting points?
What accounts for the observed differences in the properties of ionic and molecular compounds?
What accounts for the observed differences in the properties of ionic and molecular compounds?
Cite physical properties of ionic compounds.
Cite physical properties of ionic compounds.
What is a polyatomic ion?
What is a polyatomic ion?
In what form do polyatomic ions often occur in nature?
In what form do polyatomic ions often occur in nature?
How do the properties of metals differ from those of both ionic and molecular compounds?
How do the properties of metals differ from those of both ionic and molecular compounds?
What specific property of metals accounts for their unusual electrical conductivity?
What specific property of metals accounts for their unusual electrical conductivity?
What properties of metals contribute to their tendency to form metallic bonds?
What properties of metals contribute to their tendency to form metallic bonds?
What is metallic bonding?
What is metallic bonding?
How can the strength of metallic bonding be measured?
How can the strength of metallic bonding be measured?
How is the VSEPR theory used to classify molecules?
How is the VSEPR theory used to classify molecules?
What molecular geometry would be expected for F2 and HF?
What molecular geometry would be expected for F2 and HF?
According to the VSEPR theory, what molecular geometries are associated with the following types of molecules?
According to the VSEPR theory, what molecular geometries are associated with the following types of molecules?
Describe the role of unshared electron pairs in predicting molecular geometries.
Describe the role of unshared electron pairs in predicting molecular geometries.
Describe the role of double bonds in predicting molecular geometries.
Describe the role of double bonds in predicting molecular geometries.
What are hybrid orbitals?
What are hybrid orbitals?
What determines the number of hybrid orbitals produced by the hybridization of an atom?
What determines the number of hybrid orbitals produced by the hybridization of an atom?
What are intermolecular forces?
What are intermolecular forces?
In general, how do these forces compare in strength with those in ionic and metallic bonding?
In general, how do these forces compare in strength with those in ionic and metallic bonding?
What types of molecules have the strongest intermolecular forces?
What types of molecules have the strongest intermolecular forces?
What is the relationship between electronegativity and the polarity of a chemical bond?
What is the relationship between electronegativity and the polarity of a chemical bond?
What are dipole-dipole forces?
What are dipole-dipole forces?
What determines the polarity of a molecule?
What determines the polarity of a molecule?
What is meant by an induced dipole?
What is meant by an induced dipole?
What is the everyday importance of the induced dipole?
What is the everyday importance of the induced dipole?
What is hydrogen bonding?
What is hydrogen bonding?
What accounts for hydrogen bonding extraordinary strength?
What accounts for hydrogen bonding extraordinary strength?
What are London dispersion forces?
What are London dispersion forces?
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Study Notes
Chemical Bonds
- Chemical bond: Mutual electrical attraction between nuclei and valence electrons of different atoms.
- Types of bonds:
- Ionic: Strongest (50-100% ionic character); formed by electrical attraction between cations and anions; electronegativity difference of 1.7-3.3.
- Polar Covalent: Moderate (5-50% ionic character); unequal sharing of electrons; electronegativity difference of 0.3-1.7.
- Non-Polar Covalent: Weakest (0-5% ionic character); equal sharing of electrons; electronegativity difference of 0-0.3.
Electronegativity Relationships
- Greater electronegativity difference results in higher ionic character.
- Polar bonds arise from unequal attraction for shared electrons due to differing electronegativities.
Molecular Structure
- Molecule: Neutral group of atoms held by covalent bonds.
- Bond length is determined by the lowest potential energy between atoms.
- Inverse relationship between bond energy and bond length; longer bonds generally have lower energy.
- Electrons in a covalent bond are positioned between the bonding atom nuclei.
- Lone pairs: Electron pairs not involved in bonding.
Octet Rule and Lewis Structures
- Octet rule: Atoms achieve stable electron configurations by filling outer s and p orbitals, minimizing potential energy.
- Central atom in Lewis structures: Typically the least electronegative atom, with exceptions for Carbon and Hydrogen.
- Types of covalent bonds:
- Single bond: Shares one pair of electrons.
- Double bond: Shares two pairs of electrons.
- Triple bond: Shares three pairs of electrons.
Ionic Compounds
- Ionic compounds consist of equal numbers of positive and negative ions.
- Common form: Crystalline solids.
- Formula unit: Simplest ratio of ions; for CaF2, it includes one calcium cation and two fluoride anions.
- Lattice energy measures energy released when one mole of ionic gas crystallizes; greater lattice energy means stronger ionic bonding.
Properties Comparison
- Ionic compounds have higher melting and boiling points compared to molecular compounds, making them harder to vaporize.
- Physical properties of ionic compounds: Brittle, solid at room temperature, hard, soluble in water, high melting/boiling points.
- Metals differ from ionic and molecular compounds by being shiny, solid, malleable, ductile, and good conductors.
Metallic Bonding
- Metallic bonding involves attraction between metal atoms and surrounding sea of electrons.
- Strength of metallic bonds is influenced by nuclear charge and number of delocalized electrons; measured by enthalpy of vaporization.
VSEPR Theory and Molecular Geometries
- VSEPR theory predicts molecular shapes based on electron repulsion; shapes include linear, trigonal planar, tetrahedral, trigonal-bipyramidal, and octahedral.
- Unshared electron pairs lead to bent molecular shapes due to repulsion.
- Double bonds do not alter molecular geometry compared to single bonds.
Intermolecular Forces
- Intermolecular forces are attractive forces between molecules; generally weaker than ionic and metallic bonds.
- Polar molecules experience stronger intermolecular forces (dipole-dipole).
- Induced dipoles occur when polar molecules attract electrons in nonpolar molecules.
Special Bonding Interactions
- Hydrogen bonding occurs between hydrogen and highly electronegative atoms in different molecules; accounts for unusual strength.
- London dispersion forces arise from electron movement and exist between all molecules; significant in noble gases and nonpolar molecules.
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