Chem

Compound

-Composed of two or more elements in a specific ratio. ex: H2O, The compound water has physical and chemical properties different from both hydrogen and oxygen — water's properties are a unique combination of the two elements.

Pure Substances

-Has a definite and constant composition — like salt or sugar. -Can be either an element or a compound, but the composition of a pure substance doesn't vary.

History of the Atom

-In about 600 B.C. Thales of Miletus discovered that a piece of amber, after rubbing it with fur, attracts bits of hair and feathers and other light objects. He suggested that this mysterious force came from the amber. Thales, however, did not connect this force with any atomic particle. -460 B.C., a Greek philosopher, Democritus, develop the idea of atoms. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms. This idea was rejected by Aristotle, therefore everyone else rejected it. -In the 1800's an English chemist, John Dalton performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental. -In 1897, the English physicist J.J. Thomson discovered the electron and proposed a model for the structure of the atom. Thomson knew that electrons had a negative charge and thought that matter must have a positive charge. His model looked like raisins stuck on the surface of a lump of pudding. -In 1900 Max Planck, a professor of theoretical physics in Berlin showed that when you vibrate atoms strong enough, such as when you heat an object until it glows, you can measure the energy only in discrete units. He called these energy packets, quanta. -Physicists at the time thought that light consisted of waves but, according to Albert Einstein, the quanta behaved like discrete particles. Physicists call Einstein's discrete light particle, a "photon*." -Atoms not only emit photons, but they can also absorb them. In 1905, Albert Einstein wrote a ground-breaking paper that explained that light absorption can release electrons from atoms, a phenomenon called the "photoelectric effect." -Other particles got discovered around this time called alpha rays. These particles had a positive charge and physicists thought that they consisted of the positive parts of the Thompson atom (now known as the nucleus of atoms). -In 1911 Ernest Rutherford thought it would prove interesting to bombard atoms with these alpha rays, figuring that this experiment could investigate the inside of the atom (sort of like a probe). He used Radium as the source of the alpha particles and shinned them onto the atoms in gold foil. Behind the foil sat a fluorescent screen for which he could observe the alpha particles impact. -The results of the experiments came unexpected. Most of the alpha particles went smoothly through the foil. Only an occasional alpha veered sharply from its original path, sometimes bouncing straight back from the foil! Rutherford reasoned that they must get scattered by tiny bits of positively charged matter. Most of the space around these positive centers had nothing in them. He thought that the electrons must exist somewhere within this empty space. Rutherford thought that the negative electrons orbited a positive center in a manner like the solar system where the planets orbit the sun. -Rutherford knew that atoms consist of a compact positively charged nucleus, around which circulate negative electrons at a relatively large distance. The nucleus occupies less than one thousand million millionth (10 ) of the atomic volume, but contains almost all of the atom's mass. If an atom had the size of the earth, the nucleus would have the size of a football stadium. -Not until 1919 did Rutherford finally identify the particles of the nucleus as discrete positive charges of matter. Using alpha particles as bullets, Rutherford knocked hydrogen nuclei out of atoms of six elements: boron, fluorine, sodium, aluminum, phosphorus, an nitrogen. He named them protons, from the Greek for 'first', for they consisted of the first identified building blocks of the nuclei of all elements. He found the protons mass at 1,836 times as great as the mass of the electron.But there appeared something terribly wrong with Rutherford's model of the atom. The theory of electricity and magnetism predicted that opposite charges attract each other and the electrons should gradually lose energy and spiral inward. Moreover, physicists reasoned that the atoms should give off a rainbow of colors as they do so. But no experiment could verify this rainbow.

Atomic Mass

-Measured in AMU -Helps us find out the amounts of neutrons (subtract the atomic mass from the protons)

Bohr Model of the Atom

-Nucleus: Protons and neutrons clumped together. -Orbitals (where the electrons roam): Electrons "orbit" at a fast pace, # of electrons equals the number of protons. -Atomic Number: # of protons in the nucleus. -Atomic Mass: # of protons + # of neutrons.

History of Atoms pt 4

-The visual concept of the atom now appeared as an electron "cloud" which surrounds a nucleus. The cloud consists of a probability distribution map which determines the most probable location of an electron. For example, if one could take a snap-shot of the location of the electron at different times and then superimpose all of the shots into one photo, then it might look something like the view at the top. -Chemical behavior of the elements form together to create molecules. Molecules may share electrons as the hydrogen and water molecules above illustrates. (Atoms which share electrons have the name "ions.") The outer electron shell of an atom actually does the sharing and bonding of the atoms. This in turn allows chemists to describe the interactions of chemistry. Even though the orbit model of the atom does not provide an accurate model, it works well for describing chemistry. -A mystery of the nature of the nucleus remained unsolved. The nucleus contains most of the atom's mass as well as the positive charge. The protons supposedly accounted for this mass. However, a nucleus with twice the charge of another should have twice the number of protons and twice the mass. But this did not prove correct. Rutherford speculated in 1920 that there existed electrically neutral particles with the protons that make up the missing mass but no one accepted his idea at the time. -Not until 1932 did the English physicist James Chadwick finally discover the neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name, "nucleon." -Although scientists knew that atoms of a particular element have the same number of protons, they discovered that some of these atoms have slightly different masses. They concluded that the variations in mass result, more or less, from the number of neutrons in the nucleus of the atom. Atoms of an element having the same atomic number but different atomic masses get called "isotopes" of that element. -In 1928, Paul Dirac produced equations which predicted an unthinkable thing at the time- a positive charged electron. He did not accept his own theory at the time. In 1932 in experiments with cosmic rays, Carl Anderson discovered the anti-electron, which proved Dirac's equations. Physicists call it the positron. -For each variety of matter there should exist a corresponding 'opposite' or antimatter. Physicists now know that antimatter exists. However, because matter and antimatter annihilates whenever they come in contact, it does not stay around for very long. (By the way, an unsolved problem remains as to why the universe consists of mostly regular matter and not an equal amount of antimatter. Physicists call this "symmetry breaking".) -There exists not only anti-electrons but in 1955, physicists found the anti-proton, and later the anti-neutron. This allows the existence for anti-atoms, a true form of antimatter. -When scientists found out about the atomic nucleus, they questioned why the positively charged protons should remain so close without repelling. The scientists realized that there must exist new forces at work and the secrets must lie within the nucleus. They knew that the force which holds the protons together must occur much stronger than the electromagnetic force and that the force must act over very small distances (otherwise they would have noticed this force in interactions between the nucleus and the outer electrons). -In 1932, Werner Heisenberg concluded that charged particles bounce photons of light back and forth between them. This exchange of photons provides a way for the electromagnetic forces to act between the particles. The theory says that a proton shoots a photon at the electron, and the electron shoots a photon back at the proton. These photon exchanges go on all the time, very rapidly. However, because no one can see them (measure them), Heisenberg called these exchange particles, virtual photons. (Virtual meaning, not exactly 'real'.) -In 1935 a Japanese physicist, Hideki Yukawa, suggested that exchange forces might also describe the strong force between nucleons. However, virtual photons did not have enough strength for this force, so he thought that there must exist a new kind of virtual particle. Yukawa used Heisenberg's uncertainty principle to explain that a virtual particle could exist for an extremely small fraction of a second. Since its time of existence occurs nearly exactly, there would occur a great uncertainty in the energy of the virtual particle. This uncertainty allowed the particles to exist very strongly only at certain times and the particles could slip in and out of existence. He also calculated that these particles should be about 250 times as heavy as an electron. Later, in 1947, the physicist Cecil F. Powell detected this particle and called it the "pion." -Although the pions describe the transmitters of the strong force, they do not get classed with the other force-transmitting particles, such as the photon or the W and Z particles. Pions now appear not as elementary particles but rather composites made up of "quarks." The strong force gets transmitted by the pions only at relatively larger nuclear levels. -Physicists presently think that all the forces in the universe get carried by some kind of quantum particle. This theory started in 1928 with Paul Dirac stating that photons transmit the electromagnetic force. The theory called "quantum electrodynamics," or QED, developed from work by Richard Feynman, Julian Schwinger, and Sin-Itiro in the late 1940s. The four known forces and their particles appear as follows: -From 1947 until the end of the 1950's, physicists discovered many more new particles (dozens of them). The various types of particles needed a new theory to explain their strange properties. -In 1960, Murray Gell-Mann and Yuval Ne'man independently proposed a method for classifying all the particles then known. The method became known as the Eightfold Way. What the periodic table did for the elements, the Eightfold Way did for the particles. In 1964 Gell-Mann went further and proposed the existence of a new level of elementary particles and called them "quarks" (the spelling derives from a phrase in James Joyce book, Finnegans Wake, "Three quarks for Muster Mark." -Gell-Mann thought there existed at least three types of quarks. They have the names, "up," "down," and "strange." From 1974 thru 1984 the theory predicted three more quarks called "charm," "bottom" (or beauty), and "top" (or truth). And each quark has their corresponding anti-quark. -The theory of the quark explains the existence of several particles including the nucleus of the atom. In fact the proton and neutron each get made up of three quarks and the force which holds the quarks together come from particles called "gluons." -Quarks do not exist by themselves but only in pairs (mesons) or triplets (baryons).

Significant Figures

Look for the integers that show how precise your measurement is.

Law of Multiple Proportions

The law of multiple proportions states that if two elements form more than one compound between them, the masses of one element combined with a fixed mass of the second element form in ratios of small integers.

Liquid

-Distinguished by its malleable shape (is able to form into the shape of its container), but constant volume. In a liquid, atoms are close together but not in a fixed arrangement.

Gas

-Made up of atoms that are separate. However, unlike solid & liquid, a gas has no fixed shape and volume.

The Plum Pudding Model

Electrons float around in a positive-charged material. Looks like a chocolate chip cookie

Solid

-Distinguished by a fixed structure. Its shape and volume do not change. In a solid, atoms are tightly packed together in a fixed arrangement.

Conversion Metric

K.H.D.M.D.C.M Kilo Hecto Deca Meter Deci Centi Milli

Atom

-Means uncuttable -Made of: Neutrons (0), Protons(+), and Electrons (-) -Nucleus has neutrons and protons -Electrons "orbit" the nucleus like planets (incorrect) -System of electrons, equal in number to the number of nuclear proton -Cannot describe electrons as path around a nucleus with traditional orbit ideas - Cannot know exact momentum and location of electron at any given point in time - Probability distribution of where it is likely to be; higher -->; depicted in darker color - Electron = orbital - Orbital: mathematical probability function where it is likely to find electrons - Electrons = particles that can be anywhere in the haze -You can only know the probability of where the electron is surrounding the nucleus. (orbital function)

Mixtures

-Physical combinations of pure substances that have no definite or constant composition — the composition of a mixture varies according to who prepares the mixture -Different parts of a mixture can be easily separated by physical means, such as filtration. -2 types

Physical Change

-Rearrangement of the molecules in a substance, does not change the internal structure. -Whipping egg whites (air is forced into the fluid, but no new substance is produced) -Magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves). -Boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.) -Dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.) -Dicing potatoes (cutting usually separates molecules without changing them.)

Law of Constant Composition

-States that if a compound is broken down into its constituent elements, the masses of the constituents will always have the same proportions, regardless of the quantity or source of the original substance -(States that when you break down a compound to its molecules, the ratio of the molecules will be the same, no matter how large the original compound was.) -Formulated by Joseph Proust

Law of Conservation of Mass

-States that the total mass present before a chemical reaction is the same as the total mass present after the chemical reaction; in other words, mass is conserved. -Formulated by Antoine Lavoisier

Things that disprove Dalton's theory

1. The first rule was proven incorrect when scientists divided atoms in a process called nuclear fission. 2. The second rule was proven incorrect by the discovery that not all atoms of the same element have the same mass; there are different isotopes.

J.J. Thopson's charge to mass ratio

Adjusted the electric field so that the electrostatic deflection was the same as the magnetic deflection, and was able to calculate the charge-to- mass ration of an electron using the following equation - Charge-to- mass Ration: (e/m) = E*theta*E / B^2*I -Where E is the applied electric field, theta is the angle of deflection B is the applied magnetic field, and I is the distance traveled by the cathode rays -1.76 * 10^8 Coulombs per gram

Discovery of Neutrons

In 1933, James Chadwick (1891-1974) discovered a new type of radiation that consisted of neutral particles. It was discovered that these neutral atoms come from the nucleus of the atom. This last discovery completed the atomic model.

Millikan Oil Drop Experiment

- 1909) Milikan succeeded in measuring the charge of an electron - Allowed the fin set of oil to settle through a hole into a chamber where he could observe their fall - Top and bottom of the chamber consisted of electrically charged paltes - Introduced a source of x rays which can cause creation of charges when they strike matter - Charges produced by the x rays attach to an oil droplet producing one or more charges on the droplet - When there is no voltage applied the fall of the droplets is determined by their mass and the viscosity of air through which they fall - When a voltage is applied the droplets that have negative charge would fall more slowly, stop falling, or even rise depending on the number of charges on them - By adjusting the applied voltage & by observing the droplets with both with voltage on and off -->; determined that the charges on the droplets were all multiples of a smallest value (e- = 1.6 X 10 to the -19 coulombs) -->; charge of a single electron

Chemical Change

-A change that results in a completely new chemical substances being created. -At the molecular level, chemical change involves making or breaking of bonds between atoms. -iron rusting (iron oxide forms) gasoline burning (water vapor and carbon dioxide form) -Eggs cooking (fluid protein molecules uncoil and crosslink to form a network) -Bread rising (yeast converts carbohydrates into carbon dioxide gas) -Milk souring (sour-tasting lactic acid is produced) -Suntanning (vitamin D and melanin is produced)

Homogeneous Mixture

-A homogeneous mixture, sometimes called a solution, is relatively uniform in composition; every portion of the mixture is like every other portion.

Heterogeneous Mixture

-A mixture whose composition varies from position to position within the sample.

Atomic Weight

-Average all the element's version and average all the number of neutrons (whichever integer it is closest to, means that that is the most common.)

Complex Change

-Can be broken down into many simpler steps. Some of the steps are chemical and others are physical, so the overall process can't cleanly be placed in either category. -Ex: boiling coffee involves chemical change (the delicate molecules that give coffee its flavor react with air and become new, bitter-tasting substances) and physical change (the water in the coffee is going from liquid to gaseous form).

Physical Property

-Can be observed without changing the composition of matter. -Physical properties are used to observe and describe matter. -2 types: Intensive and extensive -Intensive: bulk property, meaning that it is a physical property of a system that does not depend on the system size or the amount of material in the system. It is a property that will be the same regardless of the amount of matter. ex: temperature, color, hardness, melting point, boiling point, pressure, molecular weight, and density. -Extensive: A physical property that will change if the amount of matter changes. Additive for independent, non-interacting subsystems. The property is proportional to the amount of material in the system. ex:mass, volume, length, and total charge.

The Cathode Ray Experiment

-Cathode Ray Tube: glass tube in which most of the air has been evacuated -When the two metal plates are connected to a voltage source, the cathode (negative end) emits and invisible ray. -Cathode ray is drawn to the anode (positive end) where is passes through a hole and goes to the other end of the tube. -When the ray strikes the coated surface, it produces bright light. -When an electric field is applied, the ray is attracted to the positive end, therefore, a cathode ray must consist of negative particles (electrons). -A moving charged body behaves like a tiny magnet, and it can interact with an external magnetic field. The electrons are deflected by the magnetic field -As expected when the direction of the external magnetic field is reversed, the beam of electrons is deflected in the opposite direction

Element

-Composed of a single kind of atom. An atom is the smallest particle of an element that still has all the properties of the element.

Chemical Property

-Describes its "potential" to undergo some chemical change or reaction by virtue of its composition. -What elements, electrons, and bonding are present to give the potential for chemical change.

Discovery of the Proton

-Ernest Rutherford -Rutherford knew that alpha particles are significantly more massive than electrons and positively charged. -Rutherford predicted that particles in an alpha beam would largely pass through matter unaffected, with a small number of particles slightly deflected. The particles would only be deflected if they happened to come into contact with electrons. According to the plum pudding model, this occurrence would be very unlikely. -In order to test his hypothesis, Rutherford shot a beam of alpha particles at a thin piece of gold foil. -Around the gold foil Rutherford placed sheets of zinc sulfide. These sheets produced a flash of light when struck by an alpha particle. -However, this experiment produced results that contradicted Rutherford's hypothesis. Rutherford observed that the majority of the alpha particles went through the foil; however, some particles were slightly deflected, a small number were greatly deflected, and another small number were thrown back in nearly the direction from which they had come. -To account for these observations, Rutherford devised a model called the nuclear atom. In this model, the positive charge is held in an extremely small area called the nucleus, located in the middle of the atom. Outside of the nucleus the atom is largely composed of empty space. This model states that there were positive particles within the nucleus, but failed to define what these particles are. Rutherford discovered these particles in 1919, when he conducted an experiment that scattered alpha particles against nitrogen atoms. When the alpha particles and nitrogen atoms collided protons were released.

Rutherford's Gold Foil Experiment

-Found out what protons were 1. Fluorescent Screen: covered in Zinc sulfide, which leaves a mark when alpha particles come in contact with the foil. 2. Gold Foil 3. Alpha particles (helium nucleus), radiation source, positively charged. 4. Alpha particles are directed to the gold foil 5. Most of the alpha particles went through the foil unaffected. But some of them went off in angles that were not expected. 6. Rutherford proposed that the parts where the alpha particles reflected off, were positive because like charges repel (+/+) . He said they were clumped in the middle called the nucleus. -So the things he found out. 1. Found the nucleus 2. Nucleus is positively charged 3. Most of the mass comes from the nucleus 4. The nucleus is very tiny compared to the whole atom 5. The atom is mostly empty space

History of the Atom pt 2

-In 1912 a Danish physicist, Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen. (This began a new approach to science because for the first time rules had to fit the observation regardless of how they conflicted with the theories of the time.) -Bohr said, "Here's some rules that seem impossible, but they describe the way atoms operate, so let's pretend they're correct and use them." Bohr came up with two rules which agreed with experiment: RULE 1: Electrons can orbit only at certain allowed distances from the nucleus. RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit. -Light (photons) emit whenever an electron jumps from one orbit to another. The jumps seem to happen instantaneously without moving through a trajectory. -By the 1920s, further experiments showed that Bohr's model of the atom had some troubles. Bohr's atom seemed too simple to describe the heavier elements. In fact it only worked roughly in these cases. The spectral lines did not appear correct when a strong magnetic field influenced the atoms. -Bohr and a German physicist, Arnold Sommerfeld expanded the original Bohr model to explain these variations. According to the Bohr-Sommerfeld model, not only do electrons travel in certain orbits but the orbits have different shapes and the orbits could tilt in the presence of a magnetic field. Orbits can appear circular or elliptical, and they can even swing back and forth through the nucleus in a straight line. -The orbit shapes and various angles to the magnetic field could only have certain shapes, similar to an electron in a certain orbit. As an example, the fourth orbit in a hydrogen atom can have only three possible shapes and seven possible traits. These added states allowed more possibilities for different spectral lines to appear. This brought the model of the atom into closer agreement with experimental data. -The conditions of the state of the orbit got assigned quantum numbers. The three states discussed so far consist of: orbit number (n), orbit shape (l) and orbit tilt (m). -In 1924 an Austrian physicist, Wolfgang Pauli predicted that an electron should spin (kind of like a top) while it orbits around the nucleus. The electron can spin in either of two direction. This spin consisted of a fourth quantum number: electron spin (s).

History Of the atom pt 3

-Pauli gave a rule governing the behavior of electrons within the atom that agreed with experiment. If an electron has a certain set of quantum numbers, then no other electron in that atom can have the same set of quantum numbers. Physicists call this "Pauli's exclusion principle." It provides an important principle to this day and has even outlived the Bohr-Sommerfeld model that Pauli designed it for. -In 1924 a Frenchman named Louis de Broglie thought about particles of matter. He thought that if light can exist as both particles and waves, why couldn't atom particles also behave like waves? In a few equations derived from Einstein's famous equation, (E=mc2) he showed what matter waves would behave like if they existed at all. (Experiments later proved him correct.) -In 1926 the Austrian physicist, Erwin Schrödinger had an interesting idea: Why not go all the way with particle waves and try to form a model of the atom on that basis? His theory worked kind of like harmonic theory for a violin string except that the vibrations traveled in circles. -The world of the atom, indeed, began to appear very strange. It proved difficult to form an accurate picture of an atom because nothing in our world really compares with it. -In 1926, a German physicist, Max Born had an idea about 'psi'. Born thought they resembled waves of chance. These ripples moved along waves of chance, made up of places where particles may occur and places where no particles occurred. The waves of chance ripple around in circles when the particle appears like an electron in an atomic orbit, and they ripple back and forth when the electron orbit goes straight through the nucleus, and they ripple along in straight lines when a free particle moves through interatomic space. You can think of them as waves when traveling through space and as particles whenever they travel in circles. However, they cannot exist as both waves and particles at the same time. -Just before Schrödinger proposed his theory, a German physicist Werner Heisenberg, in 1925, had a theory of his own called matrix mechanics which also explained the behavior of atoms. The two theories seemed to have an entirely different sets of assumptions yet they both worked. Heisenberg based his theory on mathematical quantities called matrices that fit with the conception of electrons as particles whereas Schrödinger based his theory on waves. Actually, the results of both theories appeared mathematically the same. -In 1927 Heisenberg formulated an idea, which agreed with tests, that no experiment can measure the position and momentum of a quantum particle simultaneously. Scientists call this the "Heisenberg uncertainty principle." This implies that as one measures the certainty of the position of a particle, the uncertainty in the momentum gets correspondingly larger. Or, with an accurate momentum measurement, the knowledge about the particle's position gets correspondingly less.

Discovering Electrons

-The first cathode-ray tube (CRT) was invented by Michael Faraday --Cathode rays are a type of radiation emitted by the negative terminal, the cathode, and were discovered by passing electricity through nearly-evacuated glass tubes. -The radiation crosses the evacuated tube to the positive terminal, the anode. Cathode rays produced by the CRT are invisible and can only be detected by light emitted by the materials that they strike, called phosphors, painted at the end of the CRT to reveal the path of the cathode rays. -These phosphors showed that cathode rays travel in straight lines and have properties independent of the cathode material. -Cathode rays are deflected by magnetic and electric fields in a manner that is identical to negatively charged material. - J.J. Thompson concluded that cathode rays are negatively charged particles that are located in all atoms.

Dalton's Atomic Theory

1. Each chemical element is composed of extremely small particles that are indivisible and cannot be seen by the naked eye, called atoms. Atoms can neither be created nor destroyed 2. All atoms of an element are alike in mass and other properties, but the atoms of one element differ from all other elements. 3. For each compound, different elements combine in a simple numerical ratio.

However, that still does not make Daltons theory irrelevant

It correctly explains the law of conservation of mass: if atoms of an element are indestructible, then the same atom must be present after a chemical reaction as before and, and the mass must constant. Dalton's atomic theory also explains the law of constant composition: if all the atoms of an element are alike in mass and if atoms unite in fixed numerical ratios, the percent composition of a compound must have a unique value without regards to the sample analyzed. The atomic theory led to the creation of the law of multiple proportions.