2.E: Átomos, moléculas e iones (ejercicios)

 

1. Describe the experiment that provided evidence that the proton is positively charged.
2. What observation led Rutherford to propose the existence of the neutron?
3. What is the difference between Rutherford’s model of the atom and the model chemists use today?
4. If cathode rays are not deflected when they pass through a region of space, what does this imply about the presence or absence of a magnetic field perpendicular to the path of the rays in that region?
5. Describe the outcome that would be expected from Rutherford’s experiment if the charge on α particles had remained the same but the nucleus were negatively charged. If the nucleus were neutral, what would have been the outcome?
6. Describe the differences between an α particle, a β particle, and a γ ray. Which has the greatest ability to penetrate matter?

 

 

 

3. The radius of an atom is approximately 10 ⁴ times larger than the radius of its nucleus. If the radius of the nucleus were 1.0 cm, what would be the radius of the atom in centimeters? in miles?
4. The total charge on an oil drop was found to be 3.84 × 10 ⁻¹⁸ coulombs. What is the total number of electrons contained in the drop?

 

 

 

1. Complete the following table for the missing elements, symbols, and numbers of electrons.

 

 

 

Element	Symbol	Number of Electrons
molybdenum
		19
titanium
	B
		53
	Sm
helium
		14

 

 

2. Complete the following table for the missing elements, symbols, and numbers of electrons.

 

 

 

Element	Symbol	Number of Electrons
lanthanum
	Ir
aluminum
		80
sodium
	Si
		9
	Be

 

 

3. Is the mass of an ion the same as the mass of its parent atom? Explain your answer.

 

 

4. What isotopic standard is used for determining the mass of an atom?

 

 

5. Give the symbol (^A_Z X) for these elements, all of which exist as a single isotope.

 

1. beryllium
2. ruthenium
3. phosphorus
4. aluminum
5. cesium
6. praseodymium
7. cobalt
8. yttrium
9. arsenic

 

 

 

6. Give the symbol (_Z^AX) for these elements, all of which exist as a single isotope.

 

1. fluorine
2. helium
3. terbium
4. iodine
5. gold
6. scandium
7. sodium
8. niobium
9. manganese

 

 

 

7. Identify each element, represented by X, that have the given symbols.

 

1. (_{26}^{55}X)
2. (_{33}^{74}X)
3. (_{12}^{24}X)
4. (_{53}^{127}X)
5. (_{18}^{40}X)
6. (_{63}^{152}X)

 

 

 

1. The isotopes ¹³¹ I and ⁶⁰ Co are commonly used in medicine. Determine the number of neutrons, protons, and electrons in a neutral atom of each.

 

 

2. Determine the number of protons, neutrons, and electrons in a neutral atom of each isotope:

 

1. (^{97}Tc)
2. (^{113}In)
3. (^{63}Ni)
4. (^{55}Fe)

 

 

 

3. Both technetium-97 and americium-240 are produced in nuclear reactors. Determine the number of protons, neutrons, and electrons in the neutral atoms of each.

 

 

4. The following isotopes are important in archaeological research. How many protons, neutrons, and electrons does a neutral atom of each contain?

 

1. (^{207}Pb)
2. (^{16}O)
3. (^{40}K)
4. (^{137}Cs)
5. (^{40}Ar)

 

 

 

5. Copper, an excellent conductor of heat, has two isotopes: ⁶³ Cu and ⁶⁵ Cu. Use the following information to calculate the average atomic mass of copper:

 

 

 

Isotope	Percent Abundance (%)	Atomic Mass (amu)
63 Cu	69.09	62.9298
65 Cu	30.92	64.9278

 

 

Calculate the average atomic mass of silicon.

 

 

7. Complete the following table for neon. The average atomic mass of neon is 20.1797 amu.

 

 

 

Isotope	Percent Abundance (%)	Atomic Mass (amu)
20 Ne	90.92	19.99244
21 Ne	0.257	20.99395
22 Ne

 

 

8. Are (_{28}^{63} X ) and ( _{29}^{62} X ) isotopes of the same element? Explain your answer.

 

 

1. Classify each element in Conceptual Problem 1 as a metal, a nonmetal, or a semimetal. If a metal, state whether it is an alkali metal, an alkaline earth metal, or a transition metal.

 

 

2. Classify each element in Conceptual Problem 2) as a metal, a nonmetal, or a semimetal. If a metal, state whether it is an alkali metal, an alkaline earth metal, or a transition metal.

 

 

3. Classify each element as a metal, a semimetal, or a nonmetal. If a metal, state whether it is an alkali metal, an alkaline earth metal, or a transition metal.

 

1. iron
2. tantalum
3. sulfur
4. silicon
5. chlorine
6. nickel
7. potassium
8. radon
9. zirconium

 

 

 

4. Which of these sets of elements are all in the same period?

 

1. potassium, vanadium, and ruthenium
2. lithium, carbon, and chlorine
3. sodium, magnesium, and sulfur
4. chromium, nickel, and krypton

 

 

 

5. Which of these sets of elements are all in the same period?

 

1. barium, tungsten, and argon
2. yttrium, zirconium, and selenium
3. potassium, calcium, and zinc
4. scandium, bromine, and manganese

 

 

 

6. Which of these sets of elements are all in the same group?

 

1. sodium, rubidium, and barium
2. nitrogen, phosphorus, and bismuth
3. copper, silver, and gold
4. magnesium, strontium, and samarium

 

 

 

7. Which of these sets of elements are all in the same group?

 

1. iron, ruthenium, and osmium
2. nickel, palladium, and lead
3. iodine, fluorine, and oxygen
4. boron, aluminum, and gallium

 

 

 

8. Indicate whether each element is a transition metal, a halogen, or a noble gas.

 

1. manganese
2. iridium
3. fluorine
4. xenon
5. lithium
6. carbon
7. zinc
8. sodium
9. tantalum
10. hafnium
11. antimony
12. cadmium

 

 

 

9. Which of the elements indicated in color in the periodic table shown below is most likely to exist as a monoatomic gas? As a diatomic gas? Which is most likely to be a semimetal? A reactive metal?

 

 

 

10. Based on their locations in the periodic table, would you expect these elements to be malleable? ¿Por qué o por qué no?

 

1. phosphorus
2. chromium
3. rubidium
4. copper
5. aluminum
6. bismuth
7. neodymium

 

 

 

11. Based on their locations in the periodic table, would you expect these elements to be lustrous? ¿Por qué o por qué no?

 

1. sulfur
2. vanadium
3. nickel
4. arsenic
5. strontium
6. cerium
7. sodium

 

 

 

1. Ionic and covalent compounds are held together by electrostatic attractions between oppositely charged particles. Describe the differences in the nature of the attractions in ionic and covalent compounds. Which class of compounds contains pairs of electrons shared between bonded atoms?
2. Which contains fewer electrons than the neutral atom—the corresponding cation or the anion?
3. What is the difference between an organic compound and an inorganic compound?
4. What is the advantage of writing a structural formula as a condensed formula?
5. The majority of elements that exist as diatomic molecules are found in one group of the periodic table. Identify the group.
6. Discuss the differences between covalent and ionic compounds with regard to
   1. a. the forces that hold the atoms together.
   2. b. melting points.
   3. c. physical states at room temperature and pressure.
7. Why do covalent compounds generally tend to have lower melting points than ionic compounds?

 

 

 

1. The structural formula for chloroform (CHCl ₃ ) was shown in Example 2.6.2. Based on this information, draw the structural formula of dichloromethane (CH ₂ Cl ₂ ).

 

 

1. F ⁻
2. Rb ⁺
3. Ce ^{3 +}
4. Zr ^{4 +}
5. Zn ^{2 +}
6. Kr ^{2 +}
7. B ^{3 +}

 

 

 

1. Ca ^{2 +}
2. Se ²⁻
3. In ^{3 +}
4. Sr ^{2 +}
5. As ^{3 +}
6. N ³⁻
7. Tl ⁺

 

 

 

1. an oxygen ion with a −2 charge
2. a beryllium ion with a +2 charge
3. a silver ion with a +1 charge
4. a selenium ion with a +4 charge
5. an iron ion with a +2 charge
6. a chlorine ion with a −1 charge

 

 

 

1. copper ion with a +2 charge
2. a molybdenum ion with a +4 charge
3. an iodine ion with a −1 charge
4. a gallium ion with a +3 charge
5. an ytterbium ion with a +3 charge
6. a scandium ion with a +3 charge

 

 

 

1. chlorine
2. phosphorus
3. scandium
4. magnesium
5. arsenic
6. oxygen

 

 

 

1. sodium
2. selenium
3. barium
4. rubidium
5. nitrogen
6. aluminum

 

 

 

9. For each representation of a monatomic ion, identify the parent atom, write the formula of the ion using an appropriate superscript, and indicate the period and group of the periodic table in which the element is found.

 

1. (_3^7X^+ )
2. (_9^{19}X^-)
3. (_{13}^{27}X^{3+})

 

 

 

5.

 

1. 27
2. 38
3. 54
4. 28
5. 67
6. 18

 

 

 

2. Classify each compound as ionic or covalent.

 

1. Zn ₃ (PO ₄ ) ₂
2. C ₆ H ₅ CO ₂ H
3. K ₂ Cr ₂ O ₇
4. CH ₃ CH ₂ SH
5. NH ₄ Br
6. CCl ₂ F ₂

 

 

 

3. Classify each compound as ionic or covalent. Which are organic compounds and which are inorganic compounds?

 

1. CH ₃ CH ₂ CO ₂ H
2. CaCl ₂
3. Y(NO ₃ ) ₃
4. H ₂ S
5. NaC ₂ H ₃ O ₂

 

 

 

5. Give two pieces of information that we obtain from a structural formula that we cannot obtain from an empirical formula.

 

 

6. The formulas of alcohols are often written as ROH rather than as empirical formulas. For example, methanol is generally written as CH ₃ OH rather than CH ₄ O. Explain why the ROH notation is preferred.

 

7. The structural formula gives us the connectivity of the atoms in the molecule or ion, as well as a schematic representation of their arrangement in space. Empirical formulas tell us only the ratios of the atoms present. The condensed structural formula of dimethylsulfide is (CH ₃ ) ₂ S.

 

1. Write the formula for each compound.

 

1. magnesium sulfate, which has 1 magnesium atom, 4 oxygen atoms, and 1 sulfur atom
2. ethylene glycol (antifreeze), which has 6 hydrogen atoms, 2 carbon atoms, and 2 oxygen atoms
3. acetic acid, which has 2 oxygen atoms, 2 carbon atoms, and 4 hydrogen atoms
4. potassium chlorate, which has 1 chlorine atom, 1 potassium atom, and 3 oxygen atoms
5. sodium hypochlorite pentahydrate, which has 1 chlorine atom, 1 sodium atom, 6 oxygen atoms, and 10 hydrogen atoms

 

 

 

1. cadmium acetate, which has 1 cadmium atom, 4 oxygen atoms, 4 carbon atoms, and 6 hydrogen atoms
2. barium cyanide, which has 1 barium atom, 2 carbon atoms, and 2 nitrogen atoms
3. iron(III) phosphate dihydrate, which has 1 iron atom, 1 phosphorus atom, 6 oxygen atoms, and 4 hydrogen atoms
4. manganese(II) nitrate hexahydrate, which has 1 manganese atom, 12 hydrogen atoms, 12 oxygen atoms, and 2 nitrogen atoms
5. silver phosphate, which has 1 phosphorus atom, 3 silver atoms, and 4 oxygen atoms

 

 

 

 

 

1. zinc and sulfur
2. barium and iodine
3. magnesium and chlorine
4. silicon and oxygen
5. sodium and sulfur

 

 

 

1. lithium and nitrogen
2. cesium and chlorine
3. germanium and oxygen
4. rubidium and sulfur
5. arsenic and sodium

 

 

 

1. Na ₂ S ₂ O ₄
2. B ₂ H ₆
3. C ₆ H ₁₂ O ₆
4. P ₄ O ₁₀
5. KMnO ₄

 

 

 

 

 

1. Benzene (C ₆ H ₆ ) is an organic compound, and KCl is an ionic compound. The sum of the masses of the atoms in each empirical formula is approximately the same. How would you expect the two to compare with regard to each of the following? What species are present in benzene vapor?

 

1. melting point
2. type of bonding
3. rate of evaporation
4. structure

 

 

 

2. Can an inorganic compound be classified as a hydrocarbon? ¿Por qué o por qué no?

 

 

3. Is the compound NaHCO ₃ a hydrocarbon? ¿Por qué o por qué no?

 

 

4. Name each compound.

 

1. NiO
2. TiO ₂
3. N ₂ O
4. CS ₂
5. SO ₃
6. NF ₃
7. SF ₆

 

 

 

5. Name each compound.

 

1. HgCl ₂
2. IF ₅
3. N ₂ O ₅
4. Cl ₂ O
5. HgS
6. PCl ₅

 

 

 

6. For each structural formula, write the condensed formula and the name of the compound.

 

a.

 

 

b.

 

 

 

c.

 

 

d.

 

 

e.

 

 

 

7. For each structural formula, write the condensed formula and the name of the compound.

 

a.

 

 

b.

 

 

c.

 

 

d.

 

 

 

1. C _n H _{2n + 2}
2. C _n H _2n
3. C _n H _{2n − 2}

 

 

 

1. Write the formula for each compound.

 

1. dinitrogen monoxide
2. silicon tetrafluoride
3. boron trichloride
4. nitrogen trifluoride
5. phosphorus tribromide

 

 

 

2. Write the formula for each compound.

 

1. dinitrogen trioxide
2. iodine pentafluoride
3. boron tribromide
4. oxygen difluoride
5. arsenic trichloride

 

 

 

3. Write the formula for each compound.

 

1. thallium(I) selenide
2. neptunium(IV) oxide
3. iron(II) sulfide
4. copper(I) cyanide
5. nitrogen trichloride

 

 

 

4. Name each compound.

 

1. RuO ₄
2. PbO ₂
3. MoF ₆
4. Hg ₂ (NO ₃ ) ₂ ·2H ₂ O
5. WCl ₄

 

 

 

5. Name each compound.

 

1. NbO ₂
2. MoS2
3. P ₄ S ₁₀
4. Cu ₂ O
5. ReF ₅

 

 

 

6. Draw the structure of each compound.

 

1. propyne
2. ethanol
3. n-hexane
4. cyclopropane
5. benzene

 

 

 

7. Draw the structure of each compound.

 

1. 1-butene
2. 2-pentyne
3. cycloheptane
4. toluene
5. phenol

 

 

2.

 

1. Tl ₂ Se
2. NpO ₂
3. FeS
4. CuCN
5. NCl ₃

 

 

 

 

1. niobium (IV) oxide
2. molybdenum (IV) sulfide
3. tetraphosphorus decasulfide
4. copper(I) oxide
5. rhenium(V) fluoride

 

 

 

7.

 

a.