periodic+table+quiz

ES 14 Period Table Quiz Name: __Peyton Powell and Whitney Chandler__

 1. Discuss each of the periods in the Period Table. Were there any problems that the “creators” faced in arranging the elements?

. When you look at a periodic table, each of the rows is considered to be a different **period ** (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of [|atomic orbitals]. Every element in the top row (the first period) has one orbital for its [|electrons]. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.

2-6. Choose 5 of the elements we have not discussed, discuss their properties, uses and include any photos/pertinent information available. __2.__ Lead Atomic Weight: 207.2 Element Group: [|Basic Metal] Discovery: Known to the ancients, with a history dating back at least 7000 years. Mentioned in the book of Exodus. Name Origin: Anglo-Saxon: lead; symbol from Latin: plumbum. Density (g/cc): 11.35 Melting Point (°K): 600.65 Boiling Point (°K): 2013 Properties: Lead is an extremely soft, highly malleable and ductile, poor electrical conductor, resistant to corrosion, blue-white shiny metal that tarnishes to dull gray in air. Lead is the only metal in which there is zero Thomson effect. Lead is a cumulative poison. Atomic Radius (pm): 175 Atomic Volume (cc/mol): 18.3 Covalent Radius (pm): 147 Ionic Radius: 84 (+4e) 120 (+2e) Specific Heat (@20°C J/g mol): 0.159 Fusion Heat (kJ/mol): 4.77 Evaporation Heat (kJ/mol): 177.8 Debye Temperature (°K): 88.00 Pauling Negativity Number: 1.8 First Ionizing Energy (kJ/mol): 715.2 Oxidation States: 4, 2 Electronic Configuration: [Xe] 4f145d106s26p2 Lattice Structure: Face-Centered Cubic (FCC) Lattice Constant (Å): 4.950 Isotopes: Natural lead is a mixture of four stable isotopes: 204Pb (1.48%), 206Pb (23.6%), 207Pb (22.6%), and 208Pb (52.3%). Twenty-seven other isotopes are known, all radioactive. Uses: Lead is used as a sound absorber, x radiation shield, and to absorb vibrations. It is used in fishing weights, to coat the wicks of some candles, as a coolant (molten lead), as ballast, and for electrodes. Lead compounds are used in paints, insecticides, and storage batteries. The oxide is used to make leaded 'crystal' and flint glass. Alloys are used as solder, pewter, type metal, bullets, shot, antifriction lubricants, and plumbing. Sources: Lead exists in its native form, though it is rare. Lead may be obtained from galena (PbS) by a roasting process. Other common lead minerals include anglesite, cerussite, and minim. Other Facts: Alchemists believed lead to be the oldest metal. It was associated with the planet Saturn

__3.__ Boron

Atomic Number: 5

Symbol: B

Atomic Weight: 10.811 Electron Configuration: [He]2s22p1

Word Origin: Arabic Buraq; Persian Burah. These are the Arabic and Persian words for borax. Isotopes: Natural boron is 19.78% boron-10 and 80.22% boron-11.

Properties: The melting point of boron is 2079°C, its boiling/sublimation point is at 2550°C, the specific gravity of crystalline boron is 2.34, the specific gravity of the amorphous form is 2.37, and its valence is 3. Boron has interesting optical properties. The boron mineral ulexite exhibits natural fiberoptic properties. Elemental boron transmits portions of infrared light. At room temperature, it is a poor electrical conductor, but it is a good conductor at high temperatures. Boron is capable of forming stable covalently bonded molecular networks. Boron filaments have high strength, yet are lightweight. The energy band gap of elemental boron is 1.50 to 1.56 eV, which is higher than that of silicon or germanium. Although elemental boron is not considered to be a poison, assimilation of boron compounds has a cumulative toxic effect.

Uses: Boron compounds are being evaluated for treating arthritis. Boron compounds are used to produce borosilicate glass. Boron nitride is extremely hard, behaves as an electrical insulator, yet conducts heat, and has lubricating properties similar to graphite. Amorphous boron provides a green color in pyrotechnic devices. Boron compounds, such as borax and boric acid, have many uses. Boron-10 is used as a control for nuclear reactors, to detect neutrons, and as a shield for nuclear radiation.

Sources: Boron is not found free in nature, although boron compounds have been known for thousands of years. Boron occurs as borates in borax and colemanite and as orthoboric acid in certain volcanic spring waters. The primary source of boron is the mineral rasorite, also called kernite, which is found in Californa's Mojave Desert. Borax deposits are also found in Turkey. High-purity crystalline boron may be obtained by vapor phase reduction of boron trichloride or boron tribromide with hydrogen on electrically heated filaments. Boron trioxide may be heated with magnesium powder to obtain impure or amorphous boron, which is a brownish-black powder. Boron is available commercially at purities of 99.9999%.

Element Classification: Semimetal Discoverer: Sir H. Davy, J.L. Gay-Lussac, L.J. Thenard

Discovery Date: 1808 (England/France) Density (g/cc): 2.34

Appearance: hard, brittle, lustrous black semimetal Atomic Radius (pm): 98

Atomic Volume (cc/mol): 4.6 Covalent Radius (pm): 82

Ionic Radius: 23 (+3e) Specific Heat (@20°C J/g mol): 1.025

Fusion Heat (kJ/mol): 23.60 Evaporation Heat (kJ/mol): 504.5

Debye Temperature (K): 1250.00 Pauling Negativity Number: 2.04

First Ionizing Energy (kJ/mol): 800.2 Oxidation States: 3

Lattice Structure: Tetragonal Lattice Constant (Å): 8.730

Lattice C/A Ratio: 0.576

4. Neon Atomic Number: 10 Symbol: Ne Atomic Weight: 20.1797 Discovery: Sir William Ramsey, M.W. Travers 1898 (England) Electron Configuration: [He]2s22p6 Word Origin: Greek neos: new Isotopes: Natural neon is a mix of three isotopes. Five other unstable isotopes of neon are known. Properties: The melting point of neon is -248.67°C, boiling point is -246.048°C (1 atm), density of gas is 0.89990 g/l (1 atm, 0°C), density of liquid at b.p. is 1.207 g/cm3, and valence is 0. Neon is very inert, but it does form some compounds, such as with fluorine. The following ions are known: Ne+, (NeAr)+, (NeH)+, (HeNe)+. Neon is known to form an unstable hydrate. Neon plasma glows reddish orange. The discharge of neon is the most intense of the rare gases at ordinary currents and voltages.

Uses: Neon is used to make neon signs. Neon and helium are used to make gas lasers. Neon is used in lightning arrestors, television tubes, high-voltage indicators, and wave meter tubes. Liquid neon is used as a cryogenic refrigerant, as it has over 40 times the refrigerating capacity per unit volume than liquid helium and over three times that of liquid hydrogen.

Sources: Neon is a rare gaseous element. It is present in the atmosphere to the extent of 1 part per 65,000 of air. Neon is obtained by liquefaction of air and separation using fractional distillation.

Element Classification: Inert (Noble) Gas Density (g/cc): 1.204 (@ -246°C) Appearance: colorless, odorless, tasteless gas Atomic Volume (cc/mol): 16.8 Covalent Radius (pm): 71 Specific Heat (@20°C J/g mol): 1.029 Evaporation Heat (kJ/mol): 1.74 Debye Temperature (K): 63.00 Pauling Negativity Number: 0.0 First Ionizing Energy (kJ/mol): 2079.4 Oxidation States: n/a Lattice Structure: Face-Centered Cubic Lattice Constant (Å): 4.430

5. Xenon Atomic Number: 54 Symbol: Xe Atomic Weight: 131.29 Discovery: Sir William Ramsay; M. W. Travers, 1898 (England) Electron Configuration: [Kr] 5s2 4d10 5p6 Word Origin: Greek xenon, stranger; xenos, strange Isotopes: Natural xenon consists of a mixture of nine stable isotopes. An additional 20 unstable isotopes have been identified. Properties: Xenon is a noble or inert gas. However, xenon and other zero valance elements do form compounds. Although xenon is not toxic, its compounds are highly toxic due to their strong oxidizing characteristics. Some xenon compounds are colored. Metallic xenon has been produced. Excited xenon in a vacuum tube glows blue. Xenon is one of the heaviest gases; one liter of xenon weighs 5.842 grams. Uses: Xenon gas is used in electron tubes, bactericidal lamps, stobe lamps, and lamps used to excite ruby lasers. Xenon is used in applications where a high molecular weight gas is needed. The perxenates are used in analytical chemistry as oxidizing agents. Xenon-133 is useful as a radioisotope. Sources: Xenon is found in the atmosphere at levels of approximately one part in twenty million. It is commercially obtained by extraction from liquid air. Xenon-133 and xenon-135 are produced by neutron irradiation in air cooled nuclear reactors. Element Classification: Inert Gas Density (g/cc): 3.52 (@ -109Ã‚Â°C) Melting Point (K): 161.3 Boiling Point (K): 166.1 Appearance: heavy, colorless, odorless noble gas Atomic Volume (cc/mol): 42.9 Covalent Radius (pm): 131 Specific Heat (@20°C J/g mol): 0.158 Evaporation Heat (kJ/mol): 12.65 Pauling Negativity Number: 0.0 First Ionizing Energy (kJ/mol): 1170.0 Oxidation States: 7 Lattice Structure: Face-Centered Cubic Lattice Constant (Å): 6.200

6. Copper

Atomic Number: 29 Symbol: Cu Atomic Weight: 63.546 Discovery: Copper has been known since prehistoric time. It has been mined for more than 5000 years. Electron Configuration: [Ar] 4s1 3d10 Word Origin: Latin cuprum: from the isle of Cyprus, which is famed for its copper mines Properties: Copper has a melting point of 1083.4 +/- 0.2°C, boiling point of 2567°C, specific gravity of 8.96 (20°C), with a valence of 1 or 2. Copper is reddish colored and takes a bright metallic luster. It is malleable, ductile, and a good conductor of electricity and heat. It is second only to silver as an electrical conductor. Uses: Copper is widely used in the electrical industry. In addition to many other uses, copper is used in plumbing and for cookware. Brass and bronze are two important copper alloys. Copper compounds are toxic to invertebrates and are used as algicides and pesticides. Copper compounds are used in analytical chemistry, as in the use of Fehling's solution to test for sugar. American coins contain copper. Sources: Sometimes copper appears in its native state. It is found in many minerals, including malachite, cuprite, bornite, azurite, and chalcopyrite. Copper ore deposits are known in North America, South America, and Africa. Copper is obtained by smelting, leaching, and electrolysis of the copper sulfides, oxides, and carbonates. Copper is commercially available at a purity of 99.999+ %. Element Classification: Transition Metal Density (g/cc): 8.96 Melting Point (K): 1356.6 Boiling Point (K): 2840 Appearance: Malleable, ductile, reddish-brown metal Atomic Radius (pm): 128 Atomic Volume (cc/mol): 7.1 Covalent Radius (pm): 117 Ionic Radius: 72 (+2e) 96 (+1e) Specific Heat (@20°C J/g mol): 0.385 Fusion Heat (kJ/mol): 13.01 Evaporation Heat (kJ/mol): 304.6 Debye Temperature (K): 315.00 Pauling Negativity Number: 1.90 First Ionizing Energy (kJ/mol): 745.0 Oxidation States: 2, 1 Lattice Structure: Face-Centered Cubic Lattice Constant (Å): 3.610 7. Have there been improvements /changes in the periodic table since Mendeleev (spelling)?

|| || He modified the 'Periodic Law' to read that the properties of the elements vary periodically with their atomic numbers. || //Moseley's modified Periodic Law puts the elements tellerium and iodine in the right order, as it does for argon and potassium, cobalt and nickel.// || || 8-9. Present a history of the atom video from its inception by Aristotle to the present. . Use pictures/ video. Year ||~ Scientist(s) ||~ Discovery || Greek era || [|Democritus] || "by convention bitter, by convention sweet, but in reality atoms and void" || 1704 || [|Isaac Newton] || Proposed a mechanical universe with small solid masses in motion. || 1803 || [|John Dalton] || Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. || 1832 || [|Michael Faraday] || Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism. || 1859 || J. Plucker || Built one of the first gas discharge tubes ("cathode ray tube"). || 1869 || [|Dmitri Mendeleeff] || Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. || 1873 || [|James Clerk Maxwell] || Proposed electric and magnetic fields filled the void. || 1874 || [|G.J. Stoney] || Proposed that electricity was made of discrete negative particles he called "[|electrons]". (Link to info on electrons) || 1879 || [|Sir William Crookes] || Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. || 1886 || E. Goldstein || Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron. || 1895 || [|Wilhelm Roentgen] || Using a CRT he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them "X-rays". || 1896 || [|Henri Becquerel] || While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. || 1897 || [|J.J. Thomson] || Used a [|CRT] to experimentally determine the charge to mass ratio [|(e/m)] of an electron =1.759 x 108 coulombs/gram. || 1897 || [|J.J. Thomson] || Studied "canal rays" and found they were associated with the proton H+. || 1898 || [|Rutherford] || Studied radiations emitted from uranium and thorium and named them //alpha// and //beta.// || 1898 || [|Marie Sklodowska Curie] || Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. || 1900 || [|Soddy] || Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements, discovered "half-life", made initial calculations on energy released during decay. || 1900 || Max Planck || used the idea of quanta (discrete units of energy) to explain hot glowing matter. || 1903 || Nagaoka || Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle. || 1904 || Abegg || Discovered that inert gases had a stable electron configuration which lead to there chemical inactivity. || 1906 || [|Hans Geiger] || Developed an electrical device to "click" when hit with alpha particles. || 1909 || [|R.A. Millikan] || Oil drop experiment determined the charge (e=1.602 x 10-19 coulomb) and the mass (m = 9.11 x 10-28 gram) of an electron. || 1911 || [|Ernest Rutherford] || Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) [|gold foil]. He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. || 1914 || [|H.G.J. Moseley] || Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. || 1919 || Aston || Discovered the existence of isotopes through the use of a mass spectrograph. || 1922 || [|Niels Bohr] || Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. || 1923 || [|de Broglie] || Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. Supported Einstein. || 1927 || [|Heisenberg] || Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle. || 1929 || [|Cockcroft / Walton] || Built an early linear accelerator and bombarded lithium with protons to produce //alpha particles// || 1930 || [|Schrodinger] || Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. || 1930 || Paul Dirac || Proposed //anti-particles//. Anderson discovered the anti-electron (positron) in 1932 and Segre/Chamberlain detected the anti-proton in 1955. || 1932 || James Chadwick || Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. || 1938 || [|Lise Meitner], Hahn, Strassman || Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction. || 1941 - 51 || [|Glenn Seaborg] || Synthesized 6 transuranium elements and suggested a change in the layout of the periodic table. || 1942 || [|Enrico Fermi] || Conducted the first controlled chain reaction releasing energy from the atoms nucleus. || 1950's - || [|New findings/particles] || Follow this link to current theories about atomic stucture. || || || Year  ||~ Scientist(s) ||~ Discovery || Greek era || [|Democritus] || "by convention bitter, by convention sweet, but in reality atoms and void" || 1704 || [|Isaac Newton] || Proposed a mechanical universe with small solid masses in motion. || 1803 || [|John Dalton] || Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. || 1832 || [|Michael Faraday] || Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism. || 1859 || J. Plucker || Built one of the first gas discharge tubes ("cathode ray tube"). || 1869 || [|Dmitri Mendeleeff] || Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. || 1873 || [|James Clerk Maxwell] || Proposed electric and magnetic fields filled the void. || 1874 || [|G.J. Stoney] || Proposed that electricity was made of discrete negative particles he called "[|electrons]". (Link to info on electrons) || 1879 || [|Sir William Crookes] || Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. || 1886 || E. Goldstein || Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron. || 1895 || [|Wilhelm Roentgen] || Using a CRT he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them "X-rays". || 1896 || [|Henri Becquerel] || While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. || 1897 || [|J.J. Thomson] || Used a [|CRT] to experimentally determine the charge to mass ratio [|(e/m)] of an electron =1.759 x 108 coulombs/gram. || 1897 || [|J.J. Thomson] || Studied "canal rays" and found they were associated with the proton H+. || 1898 || [|Rutherford] || Studied radiations emitted from uranium and thorium and named them //alpha// and //beta.// || 1898 || [|Marie Sklodowska Curie] || Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. || 1900 || [|Soddy] || Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements, discovered "half-life", made initial calculations on energy released during decay. || 1900 || Max Planck || used the idea of quanta (discrete units of energy) to explain hot glowing matter. || 1903 || Nagaoka || Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle. || 1904 || Abegg || Discovered that inert gases had a stable electron configuration which lead to there chemical inactivity. || 1906 || [|Hans Geiger] || Developed an electrical device to "click" when hit with alpha particles. || 1909 || [|R.A. Millikan] || Oil drop experiment determined the charge (e=1.602 x 10-19 coulomb) and the mass (m = 9.11 x 10-28 gram) of an electron. || 1911 || [|Ernest Rutherford] || Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) [|gold foil]. He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. || 1914 || [|H.G.J. Moseley] || Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. || 1919 || Aston || Discovered the existence of isotopes through the use of a mass spectrograph. || 1922 || [|Niels Bohr] || Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. || 1923 || [|de Broglie] || Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. Supported Einstein. || 1927 || [|Heisenberg] || Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle. || 1929 || [|Cockcroft / Walton] || Built an early linear accelerator and bombarded lithium with protons to produce //alpha particles// || 1930 || [|Schrodinger] || Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. || 1930 || Paul Dirac || Proposed //anti-particles//. Anderson discovered the anti-electron (positron) in 1932 and Segre/Chamberlain detected the anti-proton in 1955. || 1932 || James Chadwick || Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. || 1938 || [|Lise Meitner], Hahn, Strassman || Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction. || 1941 - 51 || [|Glenn Seaborg] || Synthesized 6 transuranium elements and suggested a change in the layout of the periodic table. || 1942 || [|Enrico Fermi] || Conducted the first controlled chain reaction releasing energy from the atoms nucleus. || 1950's - || [|New findings/particles] || Follow this link to current theories about atomic stucture. || ||
 * [|**William Ramsay**] || 1894 || Discovered the Noble Gases. || //In 1894 Ramsay removed oxygen, nitrogen, water and carbon dioxide from a sample of air and was left with a gas 19 times heavier than hydrogen, very unreactive and with an unknown emission spectrum. He called this gas Argon. In 1895 he discovered helium as a decay product of uranium and matched it to the emission spectrum of an unknown element in the sun that was discovered in 1868. (helios is the Greek for Sun). He went on to discover neon, krypton and xenon, and realised these represented a new group in the Periodic Table. Ramsay was awarded a [|Nobel Prize] in 1904.// ||
 * **Henry Moseley** || 1913 || Determined the atomic number of each of the elements.
 * ^  || 1914 || Predicted that there were 3 unknown elements between aluminium and gold and concluded there were only 92 elements up to and including uranium. ||   ||
 * [|**Glenn Seaborg**] || 1940 || Synthesised transuranic elements (the elements after uranium in the periodic table) || //In 1940 uranium was bombarded with neutrons in a cyclotron to produced neptuniun (Z=93). Plutonium (Z=94) was produced from uranium and deuterium. These new elements were part of a new block of the Periodic table called Actinides. Seaborg was awarded a [|Nobel Prize] in 1951.// ||
 * ~      ||||||~  **__  [|Themes] > [|Science] > [|Physics] > [|Atomic Physics] > [|Atomic Structure] > Atomic Structure Timeline  __**  ||

10. Create a question, research, answer, re-ask, re evaluate. Submit. Who discovered the atom? How did they dicover the atom? In the 5th cent. B.C. the Greek philosophers Democritus and Leucippus proposed that matter was made up of tiny, indivisible particles they called atom, or in Greek "a-tomos". The reason why they assumed this is because nothing can come from nothing. Around 1803, John Dalton (1766-1844) developed the first useful atomic theory of matter. He imagined the atom as a sphere full of an electrically positive substance mixed with negative electron. Then in 1897, Thompson discovered the first component part of the atom: the electron, a particle with a negative electric charge. ( many other people throughout history help develope the theory of the atom but these were the first to discover the atom)

Discovery of the Atom
By the 19th century, technology had advanced greatly and many elements had been discovered to work with. Using the available elements scientist such as John Dalton and Amedeo Avogadro forced them to interact with one another. From these interactions they were able to prove the existence of the atom.