Chem U4 Chapter Rev
Metallic cobalt crystallizes in a hexagonal close-packed structure. How many neighbors will a cobalt atom have?
12
How many electrons do two atoms in a double covalent bond share? How many in a triple covalent bond?
A double covalent bond has four shared electrons (two bonding pairs); a triple covalent bond has six shared electrons (three bonding pairs).
What is a pi bond? Describe, with the aid of a diagram, how the overlap of two half-filled p atomic orbitals produces a pi bond.
A pi bond is formed by the side-by-side overlap of two half-filled p atomic orbitals to produce a pi molecular orbital. In a pi bond, the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond. See Figure 8.15.
How many neutrons are in each atom? (Chapter 4) A. silicon-30 B. magnesium-24 C. nitrogen-15 D. chromium-50
A. 16 B. 12 C. 8 D. 26
Write the electron configuration of each ion. (Chapter 7) A. oxide ion B. magnesium ion C. nitride ion D. potassium ion
A. 1s22s22p6 B. 1s22s22p6 C. 1s22s22p6 D. 1s22s22p63s23p6
Write correct electron configurations for atoms of the following elements. (Chapter 5) A. sodium B. sulfur C. phosphorus D. nitrogen
A. 1s22s22p63s1 B. 1s22s22p63s23p4 C. 1s22s22p63s23p3 D. 1s22s22p3
Write complete electron configurations for the following atoms and ions. For each group, comment on the results. A. Ar, K+,Ca2+ B. Ne, Na+, Mg2+, Al3+
A. 1s22s22p63s23p6 B. 1s22s22p6; Each has a noble-gas electron configuration
Write electron configurations for the 2+ cations of these elements. A. Fe B. Co C. Ni
A. 1s22s22p63s23p63d6 1s22s22p63s23p63d7 1s22s22p63s23p63d8
How many significant figures are in each measurement? (Chapter 3) A. 0.00052 m B. 9.8 × 104 g C. 5.050 mg D. 8.700 mL
A. 2 B. 2 C. 4 D. 4
How many electrons must each atom lose to attain a noble-gas electron configuration? A. Ca B. Al C. Li D. Ba
A. 2 B. 3 C. 1 D. 2
How many electrons must be gained by each of the following atoms to achieve a stable electron configuration? A. N B. S C. Cl D. P
A. 3 B. 2 C. 1 D. 3
How many electrons are in the 2p sublevel of an atom of each element? (Chapter 5) A. aluminum B. carbon C. fluorine D. lithium
A. 6 B. 2 C. 5 D. 0
Identify the number and kinds of atoms present in a molecule of each compound. A. ascorbic acid (vitamin C), C6H8O6 B. sucrose (table sugar), C12H22O11 C. trinitrotoluene (TNT), C7H5N3O6
A. 6 C, 8 H, 6 O B. 12 C, 22 H, 11 O C. 7 C, 5 H, 3 N, 6 O
Make the following conversions. (Chapter 3) A. 66.5 mm to micrometers B. 4 × 10−2 g to centigrams C. 5.62 mg/mL to decigrams per liter D. 85 km/h to meters per second
A. 6.65 x 104 micrometers B. 4 centigrams C. 5.62 x 10-1 decigram per liter D. 2.4 x 101 meters per second
How many electrons does each atom have? What group is each in? A. nitrogen B. lithium C. phosphorus D. barium E. bromine F. carbon
A. 7, 5A B. 3, 1A C. 15, 5A D. 56, 2A E. 35, 7A F. 6, 4A
How many valence electrons does each atom have? (Chapter 7) A. argon B. aluminum C. selenium D. beryllium
A. 8 B. 3 C. 6 D. 2
Write the formula for the ion formed when each of the following elements loses its valence electrons. A. aluminum B. lithium C. barium D. potassium E. calcium F. strontium
A. Al3+ B. Li+ C. Ba2+ D. K+ E. Ca2+ F. Sr2+
Draw an electron dot structure for each molecule and explain why it fails to obey the octet rule. A. BeF2 B. SiF6 C. ClO2 D. BF3 E. XeF2
A. Be has only 4 valence electrons. B. S has 12 valence electrons. C. Cl has only 7 valence electrons D. B has only 6 valence electrons E. Xe has 10 valence electrons
Write the formula for the ion formed when each element gains electrons and attains a noble-gas configuration. A. Br B. H C. As D. Se
A. Br- B. H- C. As3- D. Se2-
Identify the kinds of ions that form each ionic compound. A. calcium fluoride, CaF2 B. aluminum bromide, AlBr3 C. lithium oxide, Li2O D. aluminum sulfide, Al2S3 E. potassium nitride, K3N
A. Ca2+, F- B. Al3+, Br- C. Li+, O2- D. Al3+, S2- E. K+, N3-
Write the formula for the ions in the following compounds. A. KCl B. BaSO4 C. MgBr2 D. Li2CO3
A. K+, Cl- B. Ba2+, SO42- C. Mg2+, Br- D. Li+, CO32-
Give the electron configuration of the element found at each location in the periodic table. (Chapter 6) A. Group 1A, period 4 B. Group 3A, period 3 C. Group 6A, period 3 D. Group 2A, period 6
A. K, 1s22s22p63s23p64s1 B. Al, 1s22s22p63s23p1 C. S, 1s22s22p63s23p4 D. Ba, 1s22s22p63s23p63d104s24p64d105s25p66s2
What is the formula of the ion formed when the following elements gain or lose valence electrons and attain noble-gas configurations? A. sulfur B. sodium C. fluorine D. phosphorus
A. S2- B. Na+ C. F- D. P3-
Which of the following pairs of elements will not form ionic compounds? A. sulfur and oxygen B. sodium and calcium C. sodium and sulfur D. oxygen and chlorine
A. a B. b C. d
Which of the following pairs of atoms would you expect to combine chemically to form an ionic compound? A. Li and S B. O and S C. Al and O D. F and Cl E. I and K F. H and N
A. a B. c C. e
Which of the following substances are most likely not ionic? A. H2O B. Na2O C. CO2 D. CaS E. SO2 F. NH3
A. a B. c C. e D. f
Which of these compounds contain elements that do not follow the octet rule? Explain. A. NF3 B. PCl2F3 C. SF4 D. SCl2
A. b B. c Assuming only single bonds, the P and S atoms each have 10 valence electrons.
Identify the larger atom of each pair. (Chapter 6) A. calcium and barium B. silicon and sulfur C. sodium and nitrogen
A. barium B. silicon C. sodium
State the number of electrons either lost or gained in forming each ion. A. Br− B. Na+ C. As3− D. Ca2+ E. Cu+ F. H−
A. gain of 1 electron B. loss of one electron C. gain of 3 electrons D. loss of 2 electrons E. loss of 1 electron F. gain of 1 electron
Classify the following compounds as ionic or covalent. A. MgCl2 B. Na2S C. H2O D. H2S
A. ionic B. ionic C. covalent D. covalent
Use VSEPR theory to predict the shapes of the following species. A. CO2 B. SiCl4 C. SO3 D. SCl2 E. CO F. H2Se
A. linear B. tetrahedral C. trigonal planar D. bent E. linear F. bent
The spheres below represent the relative diameters of atoms or ions. Rearrange the sequences in a. and b. so the relative sizes of the particles correspond to the increasing size of the particles as shown in the illustration. See pg. 207 A. oxygen atom, oxide ion, sulfur atom, sulfide ion B. sodium atom, sodium ion, potassium atom, potassium ion
A. oxygen atom, sulfur atom, oxide ion, sulfide ion B. sodium ion, potassium ion, sodium atom, potassium atom
Write electron configurations for the 3+ cations of these elements. A. chromium B. manganese C. iron
A.1s22s22p63s23p63d3 B.1s22s22p63s23p63d4 C.1s22s22p63s23p63d5
Write electron configurations for the following and comment on the result. A. N3− B. O2− C. F− D. Ne
All are 1s22s22p6. All have the same configuration as neon.
Write electron configurations for these atoms and ions, and comment on the result. A. Ar B. Cl− C. S2− D. P3−
All have the noble-gas configuration of 1s22s22p63s23p6.
Which of the following ions has the same number of electrons as a noble gas? (Chapter 7) A. Al3+ B. O2− C. Br− D. N3−
All have the same number of electrons as a noble gas.
Describe the formation of a cation that is an exception to the octet rule. In your description, compare the electron configuration of the cation to the electron configurations of the nearest noble gases.
An atom of silver has the electron configuration 1s22s22p63s23p63d104s24p64d105s1. To achieve the configuration of the preceding noble gas, krypton, a silver atom would have to lose eleven electrons and form Ag11+. To achieve the configuration of the following noble gas xenon, a silver atom must gain seven electrons and form Ag7-. Because ions with such high charges are unlikely, silver does not achieve a noble-gas configuration. However, if a silver atom loses its 5s1 electron, the result is an outer electron configuration of eighteen electrons, written as 4s24p64d10. This configuration is favored and stable. It is known as a pseudo-noble gas configuration.
Explain why compounds containing C—N and C—O single bonds can form coordinate covalent bonds with H+ but compounds containing only C—H and C—C single bonds cannot.
An unshared pair of electrons is needed for a coordinate covalent bond. There are no unshared pairs in compounds with only C-H and C-C bonds.
What element is likely to form an ionic compound with chlorine? (Chapter 7) A. iodine B. cesium C. helium
B. cesium
Name the three crystal arrangements of closely packed metal atoms. Give an example of a metal that crystallizes in each arrangement.
Body-centered cubic: Na, K, Fe, Cr, or W; face-centered cubic: Cu, Ag, Au, Al, or Pb; hexagonal close-packed: Mg, Zn, or Cd.
Explain what is meant by bond dissociation energy.
Bond dissociation energy is defined as the energy needed to break one covalent bond.
The properties of all samples of brass are not identical. Explain.
Brass is a mixture of copper and zinc. The properties of a particular sample of brass will vary with the relative proportions of the two metals.
Describe two ways that an ion forms from an atom
By gaining or losing electrons
Why are many elements more stable as ions than they are as atoms?
By gaining or losing electrons the atoms of elements achieve a noble-gas electron configuration.
Which of these statements about the periodic table is correct? (Chapter 6) A. Elements are arranged in order of increasing atomic mass. B. A period is a horizontal row. C. Nonmetals are located on the right side of the table. I only I and II only I, II, and III I and III only II and III only
E. II and III only
What is the relationship between the number of electrons in the valence shells in an electron configuration diagram for an atom and the number of dots in the corresponding electron dot structure?
Each dot in the electron dot structure represents a valence electron in the electron configuration diagram.
Define valence electrons
Electrons in the highest occupied energy level
Name the first four halogens. What group are they in, and how many valence electrons does each have?
Fluorine, chlorine, bromine, and iodine; Group 7A, 7 valence electrons
Show the relationship between the electron dot structure of an element and the location of the element in the periodic table.
For the representative elements the number of electrons in the electron dot structure is the group number.
Name three indicators of chemical change.
Formation of a gas, a change in color or odor
Explain how hexagonal close-packed, face-centered cubic, and body-centered cubic unit cells are different from one another.
Hexagonal close-packed units cells have twelve neighbors for every atom or ion. Face-centered cubic unit cells also have twelve neighbors for every atom or ion, with an atom or ion in the center of each face. Body-centered cubic units cells have eight neighbors for every atom or ion, with an atom or ion at the center of each cube.
How do the motions of sodium ions and chloride ions in molten sodium chloride differ from the motions of these ions in sodium chloride crystals?
In sodium chloride crystals the sodium and chloride ions vibrate about fixed points; in the molten state, the ions are free to move.
What is the relationship between the magnitude of a molecule's bond dissociation energy and its expected chemical reactivity?
Increasing bond dissociation energy is linked to lower chemical reactivity.
The melting point of a compound is 1240°C. Is this compound most likely an ionic or a molecular compound?
Ionic
Describe the difference between an ionic and a covalent bond.
Ionic bonds depend on electrostatic attraction between ions. Covalent bonds depend on electrostatic attraction between shared electrons and nuclei of combining atoms.
Explain why molten MgCl2 does conduct an electric current although crystalline MgCl2 does not.
Ions are free to move in molten MgCl2.
How do isotopes of an atom differ?
Isotopes have the same number of protons and electrons, but different numbers of neutrons.
Why does an anion have a negative charge?
It has gained valence electrons.
In terms of electrons, why does a cation have a positive charge?
It has lost valence electrons.
What criteria did Mendeleev and Moseley use to arrange the elements on the periodic table?
Mendeleev arranged the elements by increasing atomic mass in vertical rows and by similarities in chemical and physical properties. Mosely arranged the elements by increasing atomic number in vertical rows and by similarities in chemical and physical properties.
Why do nonmetals tend to form anions when they react to form compounds?
Most nonmetals gain 1, 2, or 3 electrons to achieve a noble-gas electron configuration.
Explain why neon is monatomic but chlorine is diatomic.
Neon has an octet of electrons. A chlorine atom achieves an octet by sharing an electron with another chlorine atom.
Which of the following gases in Earth's atmosphere would you expect to find as molecules and which as individual atoms? Explain. A. nitrogen B. oxygen C. argon
Nitrogen and oxygen achieve stability as diatomic molecules. Argon exists as individual atoms because it has a stable noble-gas electron configuration.
An alloy is composed of two or more elements. Is an alloy a compound? Explain your answer.
No, an alloy is a homogenous mixture.
Is it accurate to describe sodium chloride (NaCl) as consisting of individual particles, each made up of one Na+ cation and one Cl− anion? Explain your answer.
No, sodium chloride is composed of equal numbers of sodium ions and chloride ions; the ions are in a 1:1 ratio. Each sodium ion is surrounded by chloride ions, and each chloride is surrounded by sodium ions.
Can you predict the coordination number of an ion from the formula of an ionic compound? Explain.
No, the packing of ions in a crystalline structure depends on a number of factors including the relative sizes of the ions. The coordination number of an element can vary from compound to compound.
Characterize a coordinate covalent bond and give an example.
One atom contributes both electrons to a coordinate covalent bond, as in CO.
In a neutral atom, the number of which two subatomic particles must always be equal?
Protons and electrons must be equal.
Write electron dot formulas for the following atoms. A. C B. Be C. O D. F E. Na F. P
See pg. 207
Using electron dot structures, draw at least two resonance structures for the nitrite ion (NO2−). The oxygens in NO2− are attached to the nitrogen.
See pg. 247
Write plausible electron dot structures for the following substances. Each substance contains only single covalent bonds. A. I2 B. OF2 C. H2S D. NI3
See pg. 247
Draw as many resonance structures as you can for HN3. (Hint: the three nitrogen atoms are bonded in a row and the hydrogen atom is bonded to a nitrogen atom at the end of the row of nitrogens)
See pg. 249
Draw the electron dot structure of formic acid, H2CO2. The carbon is the central atom, and all the atoms are attached to the carbon except for a hydrogen bonded to an oxygen.
See pg. 249
Oxalic acid, C2H2O4, is used in polishes and rust removers. Draw the electron dot structure for oxalic acid given that the two carbons are bonded together but neither of the hydrogen atoms is bonded to a carbon atom.
See pg. 249
Name some alloys that you have used or seen today.
Tableware, steel in cars and buses, high-speed dental drill bits, solder in stereos and televisions, and structural steel buildings.
How does the ionic radius of a typical anion compare with the radius for the corresponding neutral atom?
The anion is larger than the corresponding neutral atom.
What does the 5 in 3d5 represent?
The d orbitals related to the third principal energy level contains 5 electrons.
Explain why ionic compounds are electrically neutral
The positive charges balance the negative charges.
If ionic compounds are composed of charged particles (ions), why isn't every ionic compound either positively or negatively charged?
The positively charged cations exactly balance the negatively charged anions.
Explain why the properties of all steels are not identical.
The properties of the steel will vary according to its composition. In addition to iron, steel can contain varying amounts of carbon and such metals as chromium, nickel, and molybdenum.
What happens to the wavelength of light as the frequency increases?
The wavelength decreases as the frequency increases.
Most ionic substances are brittle. Why?
Their network of electrostatic attractions and repulsions forms a rigid structure.
The atoms of the noble gas elements are stable. Explain.
They have little chemical reactivity; their outermost occupied energy levels are filled.
Explain briefly why metals are good conductors of electricity.
They have many mobile valence electrons. Electrons in the current replace the electrons leaving the metal.
Name each ion in Problem 31. Identify each as an anion or a cation
bromide, anion sodium, cation arsenide, anion calcium, cation copper, cation hydride, anion
