| Chapter 4 | Review and Assessment |
Reviewing Content
4.1 Defining the Atom
(34)What is an atom?
(35)What were the limitations of Democritus’s ideas about atoms?
(36)With which of these statements would John Dalton have agreed in the early 1800s? For each, explain why or why not.
Atoms are the smallest particles of matter.
The mass of an iron atom is different from the mass of a copper atom.
Every atom of silver is identical to every other atom of silver.
A compound is composed of atoms of two or more different elements.
(37)Use Dalton’s atomic theory to describe how atoms interact during a chemical reaction.
4.2 Structure of the Nuclear Atom
(38)What experimental evidence did Thomson have for each statement?
(39)Would you expect two electrons to attract or repel each other?
(40)How do the charge and mass of a neutron compare to the charge and mass of a proton?
(41)Why does it make sense that if an atom loses electrons, it is left with a positive charge?
(42)Describe the location of the electrons in Thomson’s “plum pudding” model of the atom.
(43)How did the results of Rutherford’s gold-foil experiment differ from his expectations?
(44)What is the charge, positive or negative, of the nucleus of every atom?
(45)In the Rutherford atomic model, which subatomic particles are located in the nucleus?
4.3 Distinguishing Among Atoms
(46)Why is an atom electrically neutral?
(47)What does the atomic number of each atom represent?
(48)How many protons are in the nuclei of the following atoms?
phosphorus
molybdenum
aluminum
cadmium
chromium
lead
(49)What is the difference between the mass number and the atomic number of an atom?
(50)Complete the following table by referring to Figure 4.11 on page 118.
(51)Name two ways that isotopes of an element differ.
(52)How can there be more than 1000 different atoms when there are only about 100 different elements?
(53)What data must you know about the isotopes of an element to calculate the atomic mass of the element?
(54)How is an average mass different from a weighted average mass?
(55)What is the atomic mass of an element?
(56)How are the elements arranged in the modern periodic table?
(57)Look up the word periodic in the dictionary. Propose a reason for the naming of the periodic table.
Understanding Concepts
(58)Characterize the size of an atom.
(59)Compare the size and density of an atom with its nucleus.
(60)Imagine you are standing on the top of a boron-11 nucleus. Describe the numbers and kinds of subatomic particles you would see looking down into the nucleus, and those you would see looking out from the nucleus.
(61)What parts of Dalton's atomic theory no longer agree with the current picture of the atom?
(62)Millikan measured the quantity of charge carried by an electron. How did he then calculate the mass of an electron?
(63)How is the number of electrons for a neutral atom of a given element related to the atomic number of that element?
(64)How is the atomic mass of an element calculated from isotope data?
(65)The four isotopes of lead are shown below, each with its percent by mass abundance and the composition of its nucleus. Using these data, calculate the approximate atomic mass of lead.
(66)Dalton’s atomic theory was not correct in every detail. Should this be taken as a criticism of Dalton as a scientist? Explain.
(67)Why are atoms considered the basic building blocks of matter even though smaller particles, such as protons and electrons, exist?
(68)The following table shows some of the data collected by Rutherford and his colleagues during their gold-foil experiment.
What percentage of the alpha particle deflections were 5° or less?
What percentage of the deflections were 15° or less?
What percentage of the deflections were 60° or greater?
(69)Using the data for nitrogen listed in Table 4.3, calculate the weighted average atomic mass of nitrogen. Show your work.
(70)What characteristics of cathode rays led Thomson to conclude that the rays consisted of negatively charged particles?
(71)If you know the atomic number and mass number of an atom of an element, how can you determine the number of protons, neutrons, and electrons in that atom?
(72)What makes isotopes of the same element chemically alike?
(73)In the periodic table, what happens to the pattern of properties within a period when you move from one period to the next?
Critical Thinking
(74)The diagram below shows gold atoms being bombarded with fast-moving alpha particles.
The large yellow spheres represent gold atoms. What do the small gray spheres represent?
List at least two characteristics of the small gray spheres.
Which subatomic particle cannot be found in the area represented by the gray spheres?
(75)How could you modify Rutherford’s experimental procedure to determine the relative sizes of different nuclei?
(76)Rutherford’s atomic theory proposed a dense nucleus surrounded by very small electrons. This implies that atoms are composed mainly of empty space. If all matter is mainly empty space, why is it impossible to walk through walls or pass your hand through your desk?
(77)This chapter illustrates the scientific method in action. What happens when new experimental results cannot be explained by the existing theory?
(78)Do you think there are more elements left to be discovered? Explain your answer.
(79)The law of conservation of mass was introduced in Chapter 2. Use Dalton’s atomic theory to explain this law.
Concept Challenge
(80)Diamond and graphite are both composed of carbon atoms. The density of diamond is 3.52 g/cm3. The density of graphite is 2.25 g/cm3. In 1955, scientists successfully made diamond from graphite. Using the relative densities, imagine what happens at the atomic level when this change occurs. Then suggest how this synthesis may have been accomplished.
(81)Lithium has two naturally occurring isotopes. Lithium-6 has an atomic mass of 6.015 amu; lithium-7 has an atomic mass of 7.016 amu. The atomic mass of lithium is 6.941 amu. What is the percentage of naturally occurring lithium-7?
(82)When the masses of the particles that make up an atom are added together, the sum is always larger than the actual mass of the atom. The missing mass, called the mass defect, represents the matter converted into energy when the nucleus was formed from its component protons and neutrons. Calculate the mass defect of a chlorine-35 atom by using the data in Table 4.1. The actual mass of a chlorine-35 atom is 5.81 × 10−23 g.
Cumulative Review
(83)How does the goal of pure chemistry compare with that of applied chemistry? (Chapter 1)
(84)How does a scientific law differ from a scientific theory? (Chapter 1)
(85)Classify each as an element, a compound, or a mixture. (Chapter 2)
sulfur
salad oil
newspaper
orange
(86)Oxygen and hydrogen react explosively to form water. In one reaction, 6 g of hydrogen combines with oxygen to form 54 g of water. How much oxygen was used? (Chapter 2)
(87)An aquarium measures 54.0 cm × 31.10 m × 380.0 cm. How many cubic centimeters of water will this aquarium hold? (Chapter 3)
(88)What is the mass of 4.42 cm3 of platinum? The density of platinum is 22.5 g/cm3. (Chapter 3)