Chapter 8

What must be true about the change in the total potential energy of a collection of atoms for a stable compound to be formed from the elements?

What is an ionic bond?

Define the term lattice energy. In what ways does the lattice energy contribute to the stability of ionic compounds?

How is the tendency to form ionic bonds related to the IE and EA of the atoms involved?

What influence do ion size and charge have on lattice energies of ionic compounds?

What is the octet rule? What is responsible for it?

If we were to compare the first, second, third, and fourth ionization energies of aluminum, between which pair of successive ionization energies would there be the largest difference?

The Lewis symbol for an atom only accounts for electrons in the valence shell of the atom. Why are we not concerned with the other electrons?

Define bond length and bond energy.

Define bond order. How are bond energy and bond length related to bond order? Why are there these relationships?

In terms of the potential energy change, why doesn't ionic bonding occur when two nonmetals react with each other?

When acetonitrile, \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{N}:\), a molecular compound, is evaporated what type of particle is in the gas phase? How does this compare to the salt sodium chloride?

Describe what happens to the electron density around two hydrogen atoms as they come together to form an \(\mathrm{H}_{2}\). What happens to the energy of two hydrogen atoms as they approach each other? What happens to the spins of the electrons?

What factors control the bond length in a covalent bond?

How many covalent bonds are normally formed by (a) hydrogen, (b) carbon, (c) oxygen, (d) nitrogen, and (e) chlorine?

What is a polar covalent bond?

Define dipole moment in the form of an equation. What is the value of the debye (with appropriate units)?

Define electronegativity. On what basis did Pauling develop his scale of electronegativities?

Which element has the highest electronegativity? Which is the second most electronegative element? What are the horizontal and vertical periodic trends associated with electronegativity?

Among the following bonds, which are more ionic than covalent? (a) \(\mathrm{Si}-\mathrm{O}\) (b) \(\mathrm{Ba}-\mathrm{O}\) (c) \(\mathrm{Se}-\mathrm{Cl}\) (d) \(\mathrm{K}-\mathrm{Br}\)

If an element has a low electronegativity, is it likely to be classified as a metal or a nonmetal? Explain your answer.

In what groups in the periodic table are the most reactive metals found? Where do we find the least reactive metals?

When we say that aluminum is more reactive than iron, which kind of reaction of these elements are we describing?

Arrange the following metals in their approximate order of reactivity (most reactive first, least reactive last) based on their locations in the periodic table: (a) iridium (b) silver (c) calcium (d) iron

Complete and balance the following equations. If no reaction occurs, write "N.R." (a) \(\mathrm{KCl}+\mathrm{Br}_{2} \longrightarrow\) (b) \(\mathrm{NaI}+\mathrm{Cl}_{2} \longrightarrow\) (c) \(\mathrm{KCl}+\mathrm{F}_{2} \longrightarrow\) (d) \(\mathrm{CaBr}_{2}+\mathrm{Cl}_{2} \longrightarrow\) (e) \(\mathrm{AlBr}_{3}+\mathrm{F}_{2} \longrightarrow\) (f) \(\mathrm{ZnBr}_{2}+\mathrm{I}_{2} \longrightarrow\)

In each pair, choose the better oxidizing agent. (a) \(\mathrm{O}_{2}\) or \(\mathrm{F}_{2}\) (b) \(A s_{4}\) or \(P_{4}\) (c) \(\mathrm{Br}_{2}\) or \(\mathrm{I}_{2}\) (d) \(\mathrm{P}_{4}\) or \(\mathrm{S}_{8}\) (e) \(\mathrm{Se}_{8}\) or \(\mathrm{Cl}_{2}\) (f) \(\mathrm{As}_{4}\) or \(\mathrm{S}_{8}\)

Why do we usually place the least electronegative element in the center of a Lewis structure?

Why do Period 2 elements never form more than four covalent bonds? Why are Period 3 elements able to exceed an octet?

Define (a) single bond, (b) double bond, and (c) triple bond.

The Lewis structure for hydrogen cyanide is \(\mathrm{H}-\mathrm{C} \equiv \mathrm{N}:\) Draw circles enclosing electrons to show that carbon and nitrogen obey the octet rule.

How many electrons are in the valence shells of (a) Be in \(\mathrm{BeCl}_{2},\) (b) \(\mathrm{B}\) in \(\mathrm{BCl}_{3}\), and (c) \(\mathrm{H}\) in \(\mathrm{H}_{2} \mathrm{O}\) ?

What is the minimum number of electrons that would be expected to be in the valence shell of \(\mathrm{As}\), in \(\mathrm{As} \mathrm{Cl}_{5}\) ?

Nitrogen and arsenic are in the same group in the periodic table. Arsenic forms both \(\mathrm{AsCl}_{3}\) and \(\mathrm{AsCl}_{5}\), but with chlorine, nitrogen only forms \(\mathrm{NCl}_{3}\). On the basis of the electronic structures of \(\mathrm{N}\) and \(\mathrm{As}\), explain why this is so.

What is the definition of formal charge? How are formal charges indicated on a structural formula?

How are formal charges for atoms in a molecule determined? The sum of the formal charges of a molecule must add up to what?

What are the formal charges on the atoms in the \(\mathrm{HCl}\) molecule? What are the actual charges on the atoms in this molecule? Are formal charges the same as actual charges?

What is a coordinate covalent bond?

Once formed, how (if at all) does a coordinate covalent bond differ from an ordinary covalent bond?

\(\mathrm{BCl}_{3}\) has an incomplete valence shell. Use Lewis structures to show how it could form a coordinate covalent bond with a water molecule.

What is a resonance hybrid? How does it differ from the resonance structures drawn for a molecule?

Draw the resonance structures of the benzene molecule. Why is benzene more stable than one would expect if the ring contained three carbon-carbon double bonds?

Polystyrene plastic is a hydrocarbon that consists of a long chain of carbon atoms joined by single bonds in which every other carbon is attached to a benzene ring. The ring is attached by replacing a hydrogen atom of benzene with a single bond to the carbon chain. Sketch a portion of a polystyrene molecule that contains five benzene rings.

Sketch the structures for (a) methane, (b) ethane, and (c) propane.

Draw the structure for a hydrocarbon that has a chain of six carbon atoms linked by single bonds. How many hydrogen atoms does the molecule have? What is the molecular formula for the compound?

In each of the following pairs of compounds, which would have the larger lattice energy: (a) \(\mathrm{CaO}\) or \(\mathrm{Al}_{2} \mathrm{O}_{3},\) (b) \(\mathrm{BeO}\) or \(\mathrm{SrO},\) (c) \(\mathrm{NaCl}\) or \(\mathrm{NaBr}\) ?

In each of the following pairs of compounds, which would have the larger lattice energy: (a) \(\mathrm{MgO}\) or \(\mathrm{CaO}\) (b) \(\mathrm{Na}_{2} \mathrm{O}\) or \(\mathrm{MgO}\) (c) \(\mathrm{Ca}_{3} \mathrm{P}_{2}\) or \(\mathrm{CaO}\) ?

Explain what happens to the electron configurations of \(\mathrm{Mg}\) and \(\mathrm{Br}\) when they react to form magnesium bromide

Describe what happens to the electron configurations of lithium and nitrogen when they react to form the lithium nitride.

What are the electron configurations of the \(\mathrm{Bi}^{3+}\) and \(\mathrm{Bi}^{5+}\) ions?

Write the abbreviated electron configuration of the \(\mathrm{Mn}^{3+}\) ion. How many unpaired electrons does the ion contain?