Audio Software icon An illustration of a 3. Software Images icon An illustration of two photographs. Images Donate icon An illustration of a heart shape Donate Ellipses icon An illustration of text ellipses. Chemical principles : the quest for insight Item Preview. EMBED for wordpress. Read Now ». This text is designed for a rigorous course in introductory chemistry. Its central theme is to challenge students to think and question while providing a sound foundation in the principles of chemistry.
Written for calculus-inclusive general chemistry courses, Chemical Principles helps students develop chemical insight by showing the connections between fundamental chemical ideas and their applications. The sixth edition has a new co-author, Leroy Laverman, and has been revised to make introductory material more manageable for students by splitting it across two chapters.
Cram Just the FACTS studyguides give all of the outlines, highlights, notes, and quizzes for your textbook with optional online comprehensive practice tests. Only Cram is Textbook Specific. Accompanys: What is that volume in liters? Anticipate It is useful to remember that 1 L is slightly more than 1 qt, so we should expect a volume of slightly less than 1.
Evaluate As expected, we need slightly less than 1. Self-Test A. It is often necessary to convert a unit that is raised to a power including negative powers. In such cases, the conversion factor is raised to the same power. A note on good practice: Units are treated like algebraic quantities and are multiplied and can- celed just like numbers.
More precisely, if a system is divided into parts and it is found that the property of the complete system has a value that is the sum of the values of the property of all the parts, then that property is extensive.
If that is not the case, then the property is intensive. In short, an intensive property is independent of the size of the sample. Volume is an extensive property: 2 kg of water occupies twice the volume of 1 kg of water.
Temperature is an intensive property, because we can take a sample of any size from a uniform bath of water and measure the same temperature Fig. The importance of the distinction is that we identify different substances by their intensive properties. Thus, we might recognize a sample as water by noting its color, density 1.
Some intensive properties are ratios of two extensive properties. Density is therefore an intensive property. We have to be aware that most properties depend on the state of matter and the conditions, such as the temperature and pressure. Units for physical quantities and temperature scales are discussed in Appendix 1B.
Therefore, we should expect a mass of 1 g to cor- respond to a volume of about 0. For 5 g, we should expect an answer close to 0. What is the volume of a balloon containing All measured quantities have some uncertainty associated with them; in science it is important to convey the degree to which we are certain of not only the values we report but also the results of calculations using those values. Notice that in Example A. Thus, the measurement 5. For example, could have 1, 2, or 3 sf.
Thus, the number When scientists measure the properties of a substance, they monitor and report the accuracy and precision of the data.
To make sure of their data, scientists usually repeat their measurements several times. The accuracy of a series of measurements is the closeness of their average value to the true value. The illustration in Fig. As the illustration suggests, even precise measurements can give inaccurate values.
More often than not, measurements are accompanied by two kinds of error. A sys- tematic error is an error present in every one of a series of repeated measurements. An example is the effect of a speck of dust on a pan, which distorts the mass of each sam- ple in the same direction the speck makes each sample appear heavier than it is. A ran- dom error is an error that varies at random and can average to zero over a series of observations.
An example is the effect of drafts of air from an open window moving a balance pan either up or down a little, decreasing or increasing the mass measurements randomly. Scientists attempt to minimize random error by making many observations and taking the average of the results. Systematic errors are much harder to identify. Thinking point: What are some means that scientists can use to identify and eliminate sys- tematic errors?
Physical properties are those that do not involve changing the identity of a substance. Chemical properties are those that involve changing the identity of a substance. Extensive properties depend on the mass of the sample; intensive properties do not. The precision of a measurement is an indication of how close together repeated measurements are; the accuracy of a measurement is its closeness to the true value. The acceleration, a, of the object, the rate of change of its velocity, is proportional to the force that it experiences: a Acceleration r force, or a r F The constant of proportionality between the force and the acceleration it produces is FIGURE A.
Both changes in velocity correspond to acceleration. The magnitude of the velocity of an object—the rate of change of position regardless of the direction of the motion—is called its speed, v. When we accelerate a car in a straight line, we change its speed, but not its direction, by applying a force through the rotation of the wheels and their contact with the road.
To stop a car, we apply a force that opposes the motion. However, a force can also act without changing the speed: if a body is forced to travel in a different direction at the same speed, it undergoes acceleration because velocity includes direction as well as magnitude. Forces important in chemistry include the electrostatic forces of attraction and repulsion between charged particles and the weaker forces between molecules.
Atomic nuclei exert forces on the electrons that surround them, and it takes energy to move those electrons from one place to another in a molecule. Rather than considering the forces directly, chemists normally focus on the energy needed to overcome them. One major exception, discussed in Major Technique 1, following Chapter 2, is in the vibra- tions of molecules, where atoms in bonds behave as though they are joined by springs that exert forces when the bonds are stretched and compressed.
The joule is named for James Joule, Acceleration, the rate of change of velocity, is proportional to applied force. An understanding of the role of energy is the key to understanding chemical phenomena and the structures of atoms and molecules. But just what is energy? The word energy is so common in everyday language that most people have a gen- eral sense of what it means; however, to get a technical answer to this question, we would have to delve into the theory of relativity, which is far beyond the scope of this book.
The greater the energy of an object, the greater its capacity to do work. The SI unit for energy is the joule J. Joule , but their abbreviations are which a lot of energy is released A.
A star next to an equation number. Kinetic energy, Ek, is the energy that a body possesses due to its signals that it appears in the list of motion. For a body of mass m traveling at a speed v, the kinetic energy is Key Equations on the Web site for this book: www. PLAN We need to decide how much energy must be supplied to reach the kinetic energy 0. Evaluate We see that a minimum of 3. More energy is needed to achieve that speed when friction and wind resistance are taken into account.
The potential energy, Ep, of an object is the energy that it possesses on account of its Potential energy is also commonly denoted V. There is no single formula for the potential energy of an force acts. However, two simple cases are important in chemistry: gravitational potential This formula applies only to objects close to the surface of the Earth. A body of mass m at a height h above the surface of the Earth has a gravitational Potential potential energy energy.
Equation 4 shows that the greater the altitude of an object, the greater is its gravitational potential energy. A note on good practice: You will sometimes see kinetic energy denoted KE and potential 0 energy denoted PE. Modern practice is to denote all physical quantities by a single letter accompanied, if necessary, by subscripts. What is the change in potential energy of the person? Notice that the potential energy decreases as the The energy due to attractions and repulsions between electric charges is of great charges approach each other.
The Coulomb potential energy is obtained in joules when the charges are in coulombs C, the SI unit of charge and their separation is in meters m. If the particles have the same charge— if they are two electrons, for instance—then the numerator Q1Q2, and therefore Ep itself, is positive, and the potential energy rises becomes more strongly positive as the particles approach each other r decreases.
If the particles have opposite charges—an electron and an atomic nucleus, for instance—then the numerator, and therefore Ep, is negative and the potential energy decreases in this case, becomes more negative as the separation of the particles decreases Fig.
We summarize this observation by saying that of the radiation. Kinetic energy and potential energy can change into each other, but their sum for a given object, whether as large as a planet or as tiny as an atom, is constant. A ball thrown up from the ground loses kinetic energy as it slows, but gains potential energy. The reverse happens as it falls back to Earth. Total energy, E potential energy. However, as it returns to Earth, its kinetic energy rises and its potential energy.
Potential energy, Ep approaches zero again. At each stage, its total energy is the same as it was when it was initially launched Fig. When it strikes the Earth, the ball is no longer isolated, and its energy is dissipated as thermal motion, the chaotic, random motion of atoms and molecules. No one has ever observed any exception to the law of conservation of energy, the observation that energy can be neither created nor destroyed.
One region of the universe—an individual atom, for instance—can lose energy, but another region must gain that energy. Chemists often refer to two other kinds of energy. The term chemical energy is used to refer to the change in energy when a chemical reaction takes place, as in the combustion of Energy and mass are equivalent and a fuel. The term thermal energy is speed of light. In this case it is shorthand for the sum of the potential and kinetic energies arising from the thermal motion of atoms, ions, and molecules.
Kinetic energy results from motion, potential energy from position. Example A. Which of these properties are physical properties and which are chemical properties? Suppose that they have been adopted into the SI cover to express the following measurements in the designated units: system.
Suppose that they have been adopted into back cover to express the following measurements in the designated the SI system. In each case, calculate the density. Indicate which A. What is the density of the metal experiments that the density of magnesium metal was 1. A chemist at Righton A. The accepted the water level rises to What is the density of the metal value for its density is 1.
Compare the precision and in grams per cubic centimeter? The international A. What is the volume of a 0. What is the density of the second liquid?
A spaceship attempting to shielding from radiation. Adequate shielding requires that the land on Mars must match its orbital speed. If the mass of the cladding provide Use spaceship is 3. How much energy could have been recovered nucleus, a sphere of radius 1. To what height, neglecting carbon atom is 2. The volume of a sphere of radius r is 43 r3.
RE, this general expression the course of a meal? That distance A. The actual energy released when an electron energy given in Exercise A. Is there an expression resembling and a proton form a hydrogen atom is Account for the difference.
The general expression for the potential energy of a. Although the complexity of the world appears bound- B. The ancient Greeks had much the same idea.
Their concept of an element is similar to our own; but, on Appendix 2D lists the names and the basis of experiments, we now know that there are actually more than elements, chemical symbols of the elements which—in various combinations—make up all the matter on Earth Fig. Clockwise from the red- brown liquid bromine are the silvery liquid mercury and the solids iodine, cadmium, red phosphorus, and copper.
Is there a point at which they would have to stop because the pieces no longer had the same properties as the whole or could they go on cutting forever? We now know that there is a point at which we have to stop. That is, matter consists of almost unimaginably tiny particles. The smallest particle of an element that can exist is called an atom. For example, the English schoolteacher who used he found that, in every sample of water, there was 8 g of oxygen for every 1 g of experimental measurements to argue that hydrogen and that, in another compound of the two elements hydrogen peroxide , matter consists of atoms.
These and related data led Dalton to develop his atomic hypothesis: 1 All the atoms of a given element are identical. This image is now known that the atoms of an element are not all exactly the same, for they can shows how information can be stored in differ slightly in mass. The yellow spheres are Modern instrumentation provides much more direct evidence of atoms than was silicon atoms arranged on a surface of available to Dalton Fig. There is no longer any doubt that atoms exist and that gold and silicon atoms in an arrangement that can be read by an STM microscope.
By , elements had been discovered or created, but in some cases in only very small amounts. For instance, when element was made, only two atoms were produced and they lasted less than a millisecond before disintegrating. All matter is made up of various combinations of the simple forms of matter called the chemical elements.
An element is a substance that consists of only one kind of atom. The positive charge of the nucleus exactly cancels the negative charge of the surrounding electrons. As a result, an atom is electrically neutral uncharged. Because each electron has a single negative charge, for each electron in an atom there is a particle inside the nucleus having a single positive charge. These positively charged particles are called protons denoted p ; their properties are given in Table B.
A proton is nearly times as heavy as an electron. Moseley knew that when elements are bombarded with rapidly moving electrons they emit x-rays. He found that the properties of the x-rays emitted by an element depend on its atomic number; and, by studying the x-rays of many elements, he was able to determine the values of Z for them.
Scientists have since determined the atomic numbers of all the known elements see the list of elements inside the back cover.
Technological advances in electronics early in the twentieth century led to the invention of the mass spectrometer, a device for determining the mass of an atom Fig. Mass spec- trometers are described more fully in Major Technique 6 after Chapter Mass spectrometry has been used to determine the masses of the atoms of all the elements.
We now know, for example, that the mass of a hydrogen atom is 1. Pump Electron Anticipate Because atoms are very tiny, we should expect a very large number. A pump is used to remove air.
As the strength of the Evaluate As anticipated, the number of atoms, 5. A note on good practice: Notice how we have converted the units that were given grams, When the path is at B, the ion detector for the mass of this sample into units that cancel here, kilograms. It is often prudent to sends a signal to the recorder.
The mass convert all units to SI base units. How many iron atoms are beam into position to strike the detector. Self-Test B.
How many gold atoms has the miner collected? In the nuclear model of the atom, the positive charge and almost all of the mass is concentrated in the tiny nucleus, and the surrounding negatively charged electrons take up most of the space. The atomic number is the number of protons in the nucleus.
In a sample of perfectly pure neon, for example, most of the atoms have mass 3. Some neon atoms, Detector signal. Others are about 21 times as heavy Fig. They realized that an atomic nucleus must contain subatomic particles other than protons and proposed that it also con- 20 21 22 tains electrically neutral particles called neutrons denoted n.
Because neutrons have no electric charge, their presence does not affect the nuclear charge or the number of Mass electrons in the atom.
Therefore, different numbers of The locations of the peaks on the x-axis neutrons in a nucleus give rise to atoms of different masses, even though the atoms tell us the relative masses of the atoms, belong to the same element.
As we can see from Table B. The total number of protons and neutrons in a nucleus is called the mass number, A, Another, better, name for the mass of the atom. A nucleus of mass number A is about A times as heavy as a hydrogen atom, number is nucleon number. Therefore, if we know that an atom is a certain number of times as heavy as a hydrogen atom, then we can infer the mass num- ber of the atom.
For example, because mass spectrometry shows that the three varieties of neon atoms are 20, 21, and 22 times as heavy as a hydrogen atom, we know that the mass numbers of the three types of neon atoms are 20, 21, and Atoms with the same atomic number belonging to the same element but with dif- The name isotope comes from the ferent mass numbers are called isotopes of the element.
An isotope is named by writing its mass number after the name of the element, as in neon, neon, and neon Its symbol is obtained by writing the mass num- ber as a superscript to the left of the chemical symbol of the element, as in 20Ne, 21Ne, and 22Ne. You will occasionally see the atomic number included as a subscript on the lower left, as in the symbol 22 10 Ne used in Fig. Because isotopes of the same element have the same number of protons and the same number of electrons, they have essentially the same chemical and physical properties.
However, the mass differences between isotopes of hydrogen are comparable to the masses of the atoms themselves, leading to noticeable differences in some physical properties Neon Neon Neon and slight variations in some of their chemical properties.
The most common 1H has no neutrons; its nucleus is a lone proton. The isotope with one neutron 2H same number of protons but different is called deuterium D and the one with two neutrons 3H is called tritium T. These three Self-Test B. On this scale, the atom itself would be [Answer: a 7, 8, 7; b 26, 30, 26] about 1 km in diameter.
These diagrams Self-Test B. Isotopes of an element have the same atomic number but different mass numbers. Their nuclei have the same number of protons but different numbers of neutrons. The groups 2 are the vertical columns, numbered 1 through The periods are the Group numbers horizontal rows, numbered 1 through 7 Period numbers. Noble gases 3 4 5 6 7 8 9 10 11 12 Period 1 is the top row—hydrogen and. Halogens Alkali metals. The main-group elements are those in Groups 1, 2, and 13 through 5 Transition metals 18, together with hydrogen.
Groups 1 and 2 make up the s block, 3—12 the 6 d block, and 13—18 the p block. Lanthanoids lanthanides. Actinoids actinides. The task is made much easier—and more interesting—by one of the most important discoveries in the history of chemistry. Chemists have found that when the elements are listed in order of their atomic number The story of the discovery of periodic and arranged in rows of certain lengths, they form families that show regular trends in relationships by Dmitri Mendeleev can properties.
The arrangement of elements that shows their family relationships is called be found in Box 1. The vertical columns of the periodic table are called groups.
These groups identify the In some versions of the periodic table, principal families of elements. The horizontal rows are called periods groups, with the noble gases belonging and are numbered from the top down. These are called blocks and, for reasons related to atomic structure Section 1. The members of the d block, with the exception of the elements in Group 12 the zinc group are called transition metals. As we shall see, these elements are transi- tional in character between the vigorously reactive metals in the s block and the less reac- In some versions of the periodic table, tive metals on the left of the p block.
The members of the f block, which is shown below the lanthanoids begin with the main table to save space , are the inner transition metals. The elements in Group 1 are called the alkali metals. All of them are soft, lustrous metals that melt at low temperatures.
They all produce hydro- gen when they come in contact with water Fig. The elements calcium Ca , strontium Sr , and barium Ba in Group 2 are called the alkaline earth metals, but the name is often extended to all the members of the group. The Group 2 metals have many properties in common with the Group 1 metals, but their reactions are less vigorous. They are so called because they combine with very few elements—they are chem- ically aloof.
Fluorine, for instance, is a very with water, producing gaseous hydrogen and heat. Potassium, as pale yellow, almost colorless gas, chlorine a yellow-green gas, bromine a red-brown shown here, reacts vigorously, liquid, and iodine a purple-black solid Fig.
All the halogens occur as diatomic Lab Video producing so much heat that the B. At the head of the periodic table, standing alone, is hydrogen. We treat it as a very special element and place it in none of the groups. Most of the elements are solid metals.
Only two elements mercury and bromine are liquids at ordinary temperatures, and only 11 are gaseous. A metal conducts electricity, has a luster, and is malleable and ductile. A nonmetal does not conduct electricity and is neither malleable nor ductile. A metalloid has the appearance of a metal but can behave chemically like a metal or a nonmetal, depending on conditions. Copper, for example, is a metal. It conducts electricity, has a luster when polished, and is malleable. It is so duc- tile that it is readily drawn out to form electrical wires.
Sulfur, on the other hand, is a nonmetal. This brittle yellow solid does not conduct electricity, cannot be hammered into thin sheets, and cannot be drawn out into wires. The distinctions between metals and metalloids and between metalloids and nonmetals are not very precise and not always made , but the metalloids are often taken to be the seven elements shown in Fig. The periodic table is a very useful summary of the properties of the elements.
Even if we have never heard of osmium Os , we can glance at the periodic table and see that it is a metal because it lies to the left of the metalloids all the d-block elements are met- als. As you work through this text and encounter a new element, it is. Boron B , although not resembling a metal in appearance, is included because it resembles silicon Si chemically. Example B. How B. Consider the numbers and types of subatomic particles. Assume that B.
Calculate three 77 protons, and 77 electrons; b 12 neutrons, 10 protons, and masses. List their group numbers in the periodic table. Identify each 76 protons, and 76 electrons; b 30 neutrons, 28 protons, and as a metal, a nonmetal, or a metalloid. List their group numbers in the periodic table, and identify each as a metal, a nonmetal, or a metalloid.
Classify each as a metal, a nonmetal, or a metalloid. Identify the normal physical state of each. Characterize their reactions with water and describe their B. Is this element a metal, a nonmetal, or a metalloid?
Is different? A part of chemistry is analysis: the discovery of which elements have combined together to form a substance. Another aspect of chemistry is synthesis: the process of combining elements to produce compounds or converting one compound into another. If the elements are the alphabet of chemistry, then the compounds are its plays, its poems, and its novels.
A binary compound consists of only two elements. For example, water is a binary compound of hydrogen and oxygen, with two hydrogen atoms for each oxygen atom.
Whatever the source of the water, it has exactly the same composition; indeed, a substance with a different ratio of atoms would not be water. Hydrogen peroxide H2O2 , for instance, has one hydrogen atom for every oxygen atom.
Organic compounds con- tain the element carbon and usually hydrogen, too. This text is designed for a rigorous course in introductory chemistry. Its central theme is to challenge students to think and question while providing a sound foundation in the principles of chemistry.
Authors: Peter W. Atkins, Loretta Jones, Leroy E.
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