Általános Kémiához ábrák, etc.
2007. ősz
ÁLTALÁNOS KÉMIA
I. éves Kémia BSc évf.
(Fizkém-en adott bemutatóból)
Cél, feladat:
A kémiai fogalomrendszer, gondolkodásmód bemutatása, s
ezzel a tételes tárgyak előkészítése.
Alapfogalmak: rendszeresen, precízen
Bonyolultabb fogalmak: halljanak róla, szokjanak a
gondolathoz, még akkor is, ha nem ért(het)ik pontosan.
Tartalom:
I. Alapfogalmak (A)
II. Az anyag atomi - molekuláris szerkezete. (B)
III. Az anyag makroszkopikus megjelenése.
IV. Elektrokémia (A)
V. Reakciókinetika (A)
VI. A kémiai kötés kvantummechanikai leírása (B)
Forma:
kréta és vetítés;
mellékletek –egyre inkább jegyzetként használható
Vizsga:
írásbeli (belépő) + szóbeli (egy A, egy B tétel)
Elérhetőség a hálón: a Kémiai Intézet honlapján, Fogarasi alatt, illetve:
http://www.chem.elte.hu/departments/elmkem/fg/oktatas/altkem/hallgato
knak-06/index.html
Vizsgatételek, 2006. ősz.
I. Alapfogalmak (A)
1. A modern kémia kialakulása: a súlyviszony-törvények, Dalton atomelmélete. Az Avogadrotétel hatása a kémiai kötésről alkotott képre. Az atomok tömege.
2. Az atom mai fogalmának kialakulása: Thompson, ill. Rutherford kísérlete; a Bohr-modell, ill. a
kvantummechanikai szemlélet. Az atom felépítése, izotópok, tömegdefektus. Relatív
atomtömegek. A mól fogalma. Az atommag összetétele.
3. Mérések és mértékegységek. Az SI-mértékrendszer, prefixumok. Származtatott mennyiségek.
Extenzív és intenzív mennyiség. Legegyszerűbb labormérések (a nyomás, térfogat, hőmérséklet
mérése).
4. Sztöchiometria I: vegyjel, képlet, reakcióegyenlet. Oldatok és koncentrációk. Ionreakciók; az
elektrolitok Arrhenius-féle elmélete. Sav-bázis-elméletek.
5. Sztöchiometria II: redoxi reakciók, oxidációs szám. Egyenletírás, félreakciók. Titrimetria.
II. Az anyag atomi - molekuláris szerkezete. (B)
6. A kvantumosság megjelenése a fizikában: a H-atom színképe, a feketetest-sugárzás, a
fotoelektromos hatás.
Atomok
7. A H-atom Bohr-modellje.
8. A mikrovilág kvantummechanikai leírása: az anyag kettős természete (az elektron mint hullám,
a fény mint részecske), a Heisenberg-féle határozatlansági elv, a Schrödinger-egyenlet.
9. A H-atom kvantummechanikai modellje: kvantumszámok, elektronspin, pályák;
elektroneloszlás.
10. Atomok elektronszerkezete és a periódusos rendszer: atompályák, pályaenergia, a Pauli-elv.
Elektronkonfigurációk.
11. A periódusos rendszer és elektronszerkezeti alapja. Atomi tulajdonságok: ionizációs energia és
elektronaffinitás. Az elektronegativitás különböző definíciói. Az atom-(ion-)rádiusz kérdése.
Molekulák:a kémiai kötés egyszerű (Lewis-féle) elmélete
12. Ionos kötés és az oktett-elv. A nemesgáz-szabály értelmezése a Born-Haber körfolyamat
tükrében. Kovalens kötés: a Lewis-képletek; rezonancia-szerkezetek.
13. A datív kötés, koordinációs komplexek; izoméria, elektronszerkezet. Lewis sav-bázis elmélete.
III. Az anyag makroszkopikus megjelenése.
III.1. Halmazállapotok és fizikai tulajdonságok (A)
Gázok
14. Az általános gáztörvény; gázkeverék: móltört, parciális nyomás. A moláris tömeg meghatározása. A
kinetikus gázelmélet alapjai: a nyomás kapcsolata az átlagos molekulasebességgel.
15. Átlagos kinetikus energia és hőmérséklet; az ekvipartíció elve. Diffúziósebesség. A sebességeloszlás
Maxwell-Boltzmann törvénye. Reális gázok.
Kondenzált fázisok: folyadékok és szilárd anyagok
16. Intermolekuláris kölcsönhatások: a három fő típus leírása.
17. Folyadékok általános jellemzése. Felületi feszültség, kompresszibilitás, viszkozitás.
18. A kristályos szerkezet: a kristályok rendszerezése; a röntgendiffrakció elve. Polimorfia.
19. Fázisátalakulások. Egyensúlyi gőznyomás és a forráspont. Kritikus hőmérséklet. Fázisdiagramok (víz és
szén-dioxid).
III.2. Többkomponensű rendszerek, az anyagi rendszerek csoportosítása. (A)
20. Valódi oldatok: az oldékonység hőmérsékletfüggése; gázok oldódása folyadékban (Henry-törvény).
Oldatok gőznyomása: a Raoult-törvény.
21. Folyadékelegyek desztillációja: kétkomponensű, ideális elegy viselkedését bemutató diagram és
számpélda. Erős eltérés az ideális viselkedéstől: azeotrop elegyek.
22. Kolligatív tulajdonságok: fagyáspont-csökkenés és forráspont-emelkedés; ozmózisnyomás.
III.3. A folyamatok energetikája (termokémia) (A)
24. Hőmennyiség és hőkapacitás. Reakcióhő, termokémiai egyenletek, a Hess-tétel. A belsőenergia.
Oldáshők. Fűtési-hűtési görbék.
25. Térfogati munka, entalpia. Entalpiadiagramok. Képződéshők, standard állapot.
III.4. A termodinamika alapjai, a folyamatok iránya, egyensúly (B)
26. Termodinamikai alapfogalmak. Az I. főtétel. A folyamatok irányát megszabó kvalitatív
elv: a "rendezetlenség" növekedése.
27. Az entrópia mint a rendezetlenség számszerű mértéke; a statisztikus értelmezés
bemutatása: kétatomos molekulák mikroállapotai. Standard moláris entrópiák,
reakcióentrópia.
28. A környezet entrópiaváltozása (kapcsolatteremtés a reakcióhővel). A II. főtétel. A
szabadentalpia definíciója; G mint a spontán változás ismérve. Képződési szabadentalpiák.
29. A kémiai egyensúly fogalma, a tömeghatás törvénye. Az egyensúly mint G minimuma. Az
egyensúlyi állandó definíciója Go alapján.
30. Az egyensúly gázokban, Kp és Kc . Az egyensúlyi összetétel eltolása: a Le Chatelier-elv.
31. Egyensúly vizes elektrolitoldatokban. A pH fogalma. A víz-ionszorzat. Gyenge savak bázisok, Ks és Kb kapcsolata konjugált párokra. pH-számítás, disszociációfok. Sóoldatok:
hidrolízis. Többértékű savak-bázisok.
32. Puffer-oldatok. disszociációja. Sav-bázis titrálások: titrálási görbe, az ekvivalencia-pont
pH-ja, indikátorok.
33. Heterogén egyensúlyok: Kp alakja gáz/szilárd egyensúly esetén; az oldhatósági szorzat.
Komplexek stabilitási állandója.
IV. Elektrokémia (A)
34. A galváncellák működési elve. Celladiagramok. Cellapotenciál, standard elektródpotenciálok
(redoxipotenciálok); a spontán redoxi folyamatok iránya.
35. A cellapotenciál termodinamikai leírása: a cellapotenciál kapcsolata a szabadentalpiával, ill. az
egyensúlyi állandóval. Függés a koncentrációtól: a Nernst-képlet. A pH mérése.
36. Az elektrolízis folyamata és kvantitatív törvénye. Bomlásfeszültség. Elektrokémia a
gyakorlatban: galvánelemek és akkumulátorok, elektrolízis az iparban.
V. Reakciókinetika (A)
37. A reakciósebesség definíciója. Reakciórend és sebességi állandó. A koncentráció időbeli
változása elsőrendű reakcióban; felezési idők.
38. A sebesség függése a hőmérséklettől: ütközési elmélet, aktiválási energia, aktivált komplex. Az
Arrhenius-egyenlet. Katalízis.
VI. A kémiai kötés kvantummechanikai leírása (B)
39. A H2 -molekula: minimum a potenciálfelületen. A molekulapálya (MO) -elmélet.
A kémia felosztása különböző lehet
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Kémia mindenhol
TOP 50 CHEMICALS:
Rank
1995
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1994
1
2
3
4
5
6
7
8
10
9
11
18
14
12
13
16
Billions of lb
1995
1994
Sulfuric acid
95.36 89.63
Nitrogen
68.04 63.91
Oxygen
53.48 50.08
Ethylene
46.97 44.60
Lime(b)
41.23 38.37
Ammonia
35.60 34.51
Phosphoric acid
26.19 25.58
Sodium hydroxide
26.19 25.11
Propylene
25.69 23.94
Chlorine
25.09 24.37
Sodium carbonate(c)
22.28 20.56
Methyl tert-butyl ether 17.62 13.61
Ethylene dichloride
17.26 16.76
Nitric acid
17.24 17.22
Ammonium nitrate(d)
15.99 17.03
Benzene
15.97 15.27
22
20
Carbon dioxide(f)
10.89
11.80
27
26
Hydrochloric acid
7.33
7.47
33
33
Acetic acid
4.68
3.98
42
43
42
43
Titanium dioxide
Acetone
2.77
2.76
2.76
2.66
50
49
Bisphenol A
1.62
1.70
Top 50 Chemical Companies in 1999
Rank
Rank
1999 1998
Company
Total sales
Company
Chemical sales
Chemical operating profits
Total sales
1999 ($ M)
Chemical sales
1999 ($ M) % of
total
Chem. Oper. profits
1999 ($ M) %
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
8
6
5
19
35
11
28
10
13
BASF (Germany)
DuPont (U.S.)
Bayer (Germany)
Dow Chemical (U.S.)
Exxon Mobil (U.S.)b
ICI (U.K.)
Shell (U.K./Netherlands)
Akzo Nobel (Netherlands)
Degussa-Hüls (Germany)c
BP Amoco (U.K.)
Total (France)c 42,069.0
Elf Aquitaine (France)
Sumimoto Chemical (Japan)
34,689.4
29,740.0
29,106.7
18,929.0
185,527.0
13,671.5
149,706.0
15,375.9
13,157.7
101,180.0
9,343.6
37,872.8
8,342.9
31,250.3
27,688 .0
20,192.5
18,600.0
13,777.0
13,671.5
12,886.0
12,323.5
10,085.8
9,392.0
22.2
9,272.2
8,136.5
90.1%
93.1
69.4
98.3
7.4
100.0
8.6
80.1
76.7
9.3
643.5
24.5
97.5
1,350.9
2,961.0
3,024.7
2,732.0
1,354.0
923.9
885.0
819.3
544.6
1,100.0
6.9
540.2
588.9
4.3
10.7
15.0
14.7
9.8
6.8
6.9
6.6
5.4
11.7
16
18
Henkel (Germany)
12,104.0
7,324.6
60.5
604.1
8.2
Nemzeti jövedelmekhez hasonlítva:
Comparative economic indicators, 2000
Hungary Slovenia
GDP (US$ bn)
45.6
18.1
GDP per head (US$ at PPP) 9,035
14,250
Slovakia
19.2
8,718
5.8
7.2
March 12, 2002 : The survey, published in a recent issue of the Society's publication, Chemical
& Engineering News (C & EN), ranks the global top 50 by their chemical sales. It also charts
their total sales, chemical operating profits and capital spending
The Consumer Law Page: Articles:
http://consumerlawpage.com/article/household-chemicals.shtml
TOP "10" HAZARDOUS HOUSEHOLD CHEMICALSBy Richard Alexander
AIR FRESHENERS: Most air fresheners interfere with your ability to smell by coating your
nasal passages with an oil film, or by releasing a nerve deadening agent. Known toxic
chemicals found in an air freshener: Formaldehyde: Highly toxic, known carcinogen. Phenol:
When phenol touches your skin it can cause it to swell, burn, peel, and break out in hives. Can
cause cold sweats,convulsions, circulatory collapse, coma and even death.
AMMONIA: It is a very volatile chemical, it is very damaging to your eyes, respiratory tract
and skin.
BLEACH: It is a strong corrosive. It will irritate or burn the skin, eyes and respiratory tract. It
may cause pulmonary edema or vomiting and coma if ingested. WARNING: never mix bleach
with ammonia it may cause fumes which can be DEADLY. NH2Cl, klóramin keletkezhet
DISHWASHER DETERGENTS: Most products contain chlorine in a dry form that is highly
concentrated.# 1 cause of child poisonings, according to poison control centers.
DRAIN CLEANER: Most drain cleaners contain lye, hydrochloric acid or trichloroethane.
Lye: Caustic, burns skin and eyes, if ingested will damage esophagus and stomach.
Hydrochloric acid: Corrosive, eye and skin irritant, damages kidneys, liver and digestive tract.
Trichloroethane: Eye and skin irritant, nervous system depressant; damages liver and kidneys.
contnd,.
FURNITURE POLISH: Petroleum Distillates: Highly flammable, can cause skin and
lung cancer. Phenol: (see Air fresheners, Phenol.) Nitrobenzene: Easily absorbed through
the skin, extremely toxic.
MOLD AND MILDEW CLEANERS: Chemicals contained are: Sodium hypochlorite:
Corrosive, irritates or burns skin and eyes, causes fluid in the lungs which can lead to coma
or death. Formaldehyde: Highly toxic, known carcinogen. Irritant to eyes, nose, throat, and
skin. May cause nausea, headaches, nosebleeds, dizziness, memory loss and shortness of
breath.
OVEN CLEANER: Sodium Hydroxide (Lye): Caustic, strong irritant, burns to both skin
and eyes. Inhibits reflexes, will cause severe tissue damage if swallowed.
ANTIBACTERIAL CLEANERS: may contain: Triclosan: Absorption through the skin
can be tied to liver damage. (Ált. fertőtlenítőszer – kórházak :
LAUNDRY ROOM PRODUCTS: Sodium or calcium hypocrite!? nyilván hypochlorite:
Highly corrosive, irritates or burns skin, eyes or respiratory tract. Linear alkylate sulfonate:
Absorbed through the skin. Known liver damaging agent. Sodium Tripolyphosphate:
Irritates skin and mucous membranes, causes vomiting. Easily absorbed through the skin
TOILET BOWL CLEANERS: Hydrochloric acid: Highly corrosive, irritant to both skin
and eyes. Damages kidneys and liver. Hypochlorite Bleach: Corrosive, irritates or burns
eyes, skin and respiratory tract. May cause pulmonary edema, vomiting or coma if ingested.
Contact with other chemicals may cause chlorine fumes which may be fatal
VÁLOGATÁSOK KURRENS EREDMÉNYEKBŐL:
September 3, 2007
Volume 85, Number 36 , p. 7
When Organics Fail, Try Water
Ladder polyethers form readily from epoxides in water
Complex ladder polyether natural products, so named for their runglike structure, are the active
toxins found in the harmful algal blooms known as red tides. Red tides cause devastating
ecological damage, so scientists hope that by studying this water-promoted cascade reaction, they
will gain a better understanding of how and why these toxins form
Mercury Fulminate Revealed
Researchers finally determine X-ray structure of infamous explosive
the super-sensitive explosive with a nefarious 300-year
history, has been so difficult to handle in the lab that only
now have scientists finally determined its crystal structure.
Wolfgang Beck and Thomas M. Klapötke, professors at Ludwig Maximilians University in
Munich, Germany, and their colleagues report that, as expected, the molecule Hg(CNO) 2 is nearly
linear, with the nitrogens carrying a positive charge and the oxygens a negative charge. The
mercury atom is bound to two carbon atoms, with the bonding arrangement O–N C– Hg–C N–O
(Z. Anorg. Allg. Chem. 2007, 633, 1417). This connectivity and linear structure was predicted by a
number of groups, including Beck's and Klapötke's. Other groups, however, had predicted that the
O atoms were bound to Hg.
Mercury fulminate is sensitive to friction, heat, and shock, and it decomposes violently
VÁLOGATÁSOK KURRENS EREDMÉNYEKBŐL:
September 6, 2004
Vol. 82, Iss. 36
INHIBITORS TARGET KEY TB ENZYME
Iminosugars may provide leads for new class of tuberculosis drugs
Scientists in England have designed and synthesized
the first inhibitors of an enzyme that is essential for
the survival of the tuberculosis bacterium [Org.
Biomol. Chem., 2, 2418 (2004)]. The compounds
might lead to better treatments for TB, which annually
infects 8 million to 10 million people and kills 2
million to 3 million. e and kills 2 million to 3 million.
October 3, 2007
Also appeared in print Oct. 8, 2007, p. 11
Inorganic Chemistry
Mercury Tetrafluoride Synthesized
Elusive Hg(IV) species has been prepared in solid argon, neon
Jyllian Kemsley
Mercury, a group 12 element with a valence electron configuration of s 2d10, is
generally considered to be limited to the +1 and +2 oxidation states. Theoretical
work, however, has long predicted that mercury could be stable in the +4 oxidation
state. In a fundamental advance that opens new possibilities for mercury
compounds, that prediction has now been confirmed with the successful synthesis
of HgF4 using matrix isolation techniques (Angew. Chem., DOI:
10.1002/anie.200703710).
SCIENCE & TECHNOLOGY
RDX LINKS RUSSIAN CRASHES
Powerful explosive found in the debris of two planes
that crashed
Traces of RDX, a common military explosive
that is also known as hexogen or cyclonite,
were found at the crash sites of two Russian
planes that went down within minutes of
each other on Aug. 24, Russian authorities
report. RDX was also used in a suicide
bombing at a Moscow metro station on Aug.
31, news reports say.
"RDX is a very powerful explosive," says
Jimmie C. Oxley, a professor of chemistry at
the University of Rhode Island. "A terrorist
wouldn't need to conceal very much." RDX
has an explosive power considerably greater
than that of TNT, is chemically stable, and is
more susceptible than TNT to shock
detonation.
"Molekuláris giroszkóp"
COMPOSITE MATERIALS
Custom blending of materials with distinct
characteristics leads to advanced composites with tailormade properties
IT'S A BIRD, IT'S A PLANE ... Advanced composite materials in the V22 Osprey's tilt-rotor system play a key role in enabling the
sophisticated plane to take off and land on aircraft carriers like a
helicopter and fly like a turboprop airplane.
SHEET MOLDING Sheets of a composite molding material can be prepared by
feeding glass or carbon fibers (chopped or intact) and a polymer-based resin
(orange trough) between a pair of plastic films
Gyönyörűszép Molekulák
One example, reported by Bryan W. Eichhorn's group at the University of Maryland, is the
[As@Ni12@As20]3– ion. This cluster consists of an As20 pentagonal dodecahedron that encapsulates a Ni12
icosahedron, which contains an arsenic atom at its center. The As20 cage is related to the smallest fullerene, C20
5, 2003
C&EN May
Source: C&EN/ April 14, 2003
MOLECULAR DESIGN
ION RECOGNITION
System exploits weak interactions to attract anion to cation in capsule
A new approach to anion recognition that uses electrostatic and hydrogenbonding interactions has been developed by chemists at the University of
Missouri, Columbia.
"For the first time, we have utilized a single molecule to completely
encapsulate an ion pair in polar media," chemistry professor Jerry L.
Atwood tells C&EN. "We envision that resins incorporating these capsules
could be used in anion sensing in environmental applications."
Atwood and postdoc Agnieszka Szumna embedded a
tetramethylammonium cation in the pocket of a resorcin[4]arene molecule
functionalized with bulky amide substituents. The complex selectively
binds to a chloride anion in solvents such as methanol [Chem. Comm.,
2003, 940].
Ezt is tudjuk ……
EPO
Understanding the function of endogenous
hormones and putting them to good use to
treat diseases has been one of the great
accomplishments of modern medicine. One
natural hormone that has turned out to be a
blockbuster drug--but not without some
controversy--is erythropoietin (EPO).
EPO is a glycoprotein (protein-sugar conjugate) that serves as the
primary regulator of red blood cells (erythrocytes) in mammals. It
stimulates bone marrow stem cells to differentiate into red blood cells
and controls hemoglobin synthesis and red blood cell concentration.
Human EPO is a 30,400-dalton molecule containing 165 amino acids
and four carbohydrate chains that incorporate sialic acid residues.
There are several forms of EPO, designated by Greek letters, that
differ only in the carbohydrate content.
In infants, EPO is produced mostly in the liver, but the kidneys become the primary site of EPO synthesis
shortly after birth. EPO production is stimulated by reduced oxygen content in arterial blood in the kidneys.
Circulating EPO binds to receptors on the surface of erythroid progenitor cells that in turn mature into red blood
cells.….. contnd
Human EPO was first isolated and later purified from urine in the
1970s. Interest in developing clinical uses for EPO led to the
discovery of the gene encoding EPO, and several groups devised
recombinant DNA methods to produce EPO by the mid-1980s.
Recombinant EPO quickly made it to market to treat anemia resulting
from a host of conditions, primarily kidney failure, HIV infection in
patients treated with AZT, and cancer chemotherapy. Doses of EPO
are given by injection one or more times per week to maintain a
normal hematocrit level, the ratio of red blood cell volume to total
blood volume. Generally, EPO might be prescribed for any condition
where blood oxygen levels are depressed and to help eliminate the
potential need for blood transfusions.
……
Enzyme immunoassays can provide a measure of serum EPO levels,
but the tests can't determine if the EPO is natural or produced
recombinantly and injected by unscrupulous athletes. The World
Anti-Doping Agency has now developed combination urine and blood
tests that can detect EPO abuse by athlet.
Az anyag atomi-molekuláris
szerkezete
Robert Boyle (1627–1691) was born at Lismore Castle, Munster,
Ireland, the fourteenth child of the Earl of Cork. As a young man of
means, he was tutored at home and on the Continent. He spent the
later years of the English Civil Wars at Oxford, reading and
experimenting with his assistants and colleagues. This group was
committed to the New Philosophy, which valued observation and
experiment at least as much as logical thinking in formulating
accurate scientific understanding. At the time of the restoration of the
British monarchy in 1660, Boyle played a key role in founding the Royal
Society to nurture this new view of science.
Although Boyle's chief scientific interest was chemistry, his first
published scientific work, New Experiments Physico-Mechanicall,
Touching the Spring of the Air and its Effects (1660), concerned the
physical nature of air, as displayed in a brilliant series of experiments
in which he used an air pump to create a vacuum. The second edition
of this work, published in 1662, delineated the quantitative
relationship that Boyle derived from experimental values, later
known as "Boyle's law": that the volume of a gas varies inversely
with pressure.
Robert Boyle at the age of thirty-seven, with his air pump in the background.
François Diodati reengraved this image from an engraving by William Faithorne, Opera varia (1680).
Courtesy Edgar Fahs Smith Memorial Collection, Department of Special Collections, University of
Pennsylvania Library.
Boyle was an advocate of corpuscularism, a form of atomism
that was slowly displacing Aristotelian and Paracelsian views
of the world. Instead of defining physical reality and
analyzing change in terms of Aristotelian substance and form
and the classical four elements of earth, air, fire, and water—
or the three Paracelsian elements of salt, sulfur, and
mercury—corpuscularism discussed reality and change in
terms of particles and their motion. Boyle believed that
chemical experiments could demonstrate the truth of the
corpuscularian philosophy. In this context he defined the
term element in Sceptical Chymist (1661): " . . . certain
primitive and simple, or perfectly unmingled bodies; which
not being made of any other bodies, or of one another, are the
ingredients of which all those called perfectly mixt bodies are
immediately compounded, and into which they are ultimately
resolved."
Robert Boyle:
The Skeptical Chemist, 1661 (!)
"Én megpróbáltam a kémiát más szempontok szerint művelni,
nem úgy, ahogy az eddigi kémikusok tették, hanem ahogy egy
tudóshoz illik." ....
"Bár viselnék az emberek inkább a tudományok előrehaladását
szívükön, mint önző érdeküket, akkor könnyen belátnák, hogy
nagyobb szolgálatot tennének a világnak, ha minden erejüket
kísérletek végzésére és megfigyelések gyűjtésére fordítanák,
ahelyett hogy kísérleti alapozás nélküli elméleteket állítanának
fel. "
The Burning lenses
Calcination of a piece of metal with the burning lenses
Joseph Louis Proust
(1754 – 1826)
Állandó súlyviszonyok törvénye
John Dalton
(1766 – 1844)
Többszörös súlyviszonyok törvénye
Joseph Louis Gay-Lussac’s law of combining volumes (1808) (when
two gases react, the volumes of the reactants and products—if gases—
are in whole number ratios) tended to support Dalton’s atomic theory.
Dalton did not in fact accept Gay-Lussac's work, but the Italian chemist
Amedeo Avogadro (1776–1856) saw it as the key to a better
understanding of molecular constituency.
Amedeo Avogadro.
In 1811 Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal
numbers of molecules. From this hypothesis it followed that relative molecular weights of any two gases are the
same as the ratio of the densities of the two gases under the same conditions of temperature and pressure. Avogadro
also astutely reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of
two or more atoms. (Avogadro did not actually use the word atom; at the time the words atom and molecule were
used almost interchangeably. He talked about three kinds of "molecules," including an "elementary molecule"—what
we would call an atom.) Thus Avogadro was able to overcome the difficulty that Dalton and others had encountered
when Gay-Lussac reported that above 100oC the volume of water vapor was twice the volume of the oxygen used to
form it. According to Avogadro, the molecule of oxygen had split into two atoms in the course of forming water
vapor.
Curiously, Avogadro's hypothesis was neglected for half a century after it was first published. Many reasons for this
neglect have been cited, including some theoretical problems, such as Jöns Jakob Berzelius's "dualism," which
asserted that compounds are held together by the attraction of positive and negative electrical charges, making it
inconceivable that a molecule composed of two electrically similar atoms—as in oxygen—could exist. In addition,
Avogadro was not part of an active community of chemists: the Italy of his day was far from the centers of chemistry
in France, Germany, England, and Sweden, where Berzelius was based.
Avogadro was a native of Turin, where his father, Count Filippo Avogadro, was a lawyer and government leader in
the Piedmont (Italy was then still divided into independent countries). Avogadro succeeded to his father's title, earned
degrees in law, and began to practice as an ecclesiastical lawyer. After obtaining his formal degrees, he took private
lessons in mathematics and sciences, including chemistry. For much of his career as a chemist he held the chair of
physical chemistry at the University of Turin.
Avogadro EREDETI CIKKEBOL! : http://web.lemoyne.edu/~giunta/avogadro.html
A TELJES SZOVEGET FILE-BAN ELTETTEM: avogadro-original
Essay on a Manner of Determining the Relative Masses of the Elementary Molecules of Bodies, and the Proportions in
Which They Enter into These Compounds
Journal de Physique 73, 58-76 (1811) [Alembic Club Reprint No. 4] I.
M. Gay-Lussac has shown in an interesting Memoir (Mémoires de la Société d'Arcueil, Tome
II.) that gases always unite in a very simple proportion by volume, and that when the result of
the union is a gas, its volume also is very simply related to those of its components. But the
quantitative proportions of substances in compounds seem only to depend on the relative number of molecules which combine, and
on the number of composite molecules which result. It must then be admitted that very simple relations also exist between the
volumes of gaseous substances and the numbers of simple or compound molecules which form them. Kiemeles FG: The
first
hypothesis to present itself in this connection, and apparently even the only admissible one, is
the supposition that the number of integral molecules in any gases is always the same for equal
volumes, or always proportional to the volumes. Indeed, if we were to suppose that the number of molecules
contained in a given volume were different for different gases, it would scarcely be possible to conceive that the law regulating the
distance of molecules could give in all cases relations as simple as those which the facts just detailed compel us to acknowledge
between the volume and the number of molecules. On the other hand, it is very well conceivable that the molecules of gases being
at such a distance that their mutual attraction cannot be exercised, their varying attraction for caloric may be limited to condensing
the atmosphere formed by this fluid having any greater extent in the one case than in the other, and, consequently, without the
distance between the molecules varying; or, in other words, without the number of molecules contained in a given volume being
different. Dalton, it is true, has proposed a hypothesis directly opposed to this, namely that the quantity of caloric is always the
same for the molecules of all bodies whatsoever in the gaseous state, and that the greater or less attraction for caloric only results in
producing a greater or less condensation of this quantity around the molecules, and thus varying the distance between the
molecules themselves. But in our present ignorance of the manner in which this attraction of the molecules for caloric is exerted,
there is nothing to decide us à priori in favour of the one of these hypotheses rather than the other; and we should rather be inclined
to adopt a neutral hypothesis, which would make the distance between the molecules and the quantities of caloric vary according to
unknown laws, were it not that the hypothesis we have just proposed is based on that simplicity of relation between the volumes of
gases on combination, which would appear to be otherwise inexplicable.
Maxwell, around 1875, describing atoms:
"foundation stones of the material universe ...
unbroken and unworn. They continue to this day as
they were createdperfect in number and measure
and weigth."
(Scientific American, Aug. 1997, p. 73.)
Az atom mai fogalmának kialakulása
Feltörik a diót
Az első csapás az oszthatatlan atomra:
J.J. Thomson, 1897: az elektron felfedezése
A pudding-modell:
Rutherford, 1911: az atommag
A kvantumosság megjelenése
a fizikában:
1. a H-atom színképe,
2. feketetest-sugárzás,
3. fotoelektromos effektus
Színképek
Folytonos spektrum
Vonalas emissziós sp.
Vonalas abszorpciós sp.
A spektroszkópia alapja: a fényt komponenseire bontjuk
Angstrom svéd (asztro)fizikus:
az atomos hidrogén spektruma a látható fény tartományában
Négy vonalat észlelt: 410 nm, 434 nm, 486 nm, and 656 nm.
Anders Ångström (1817-1874)
One of the leading founders of the science
of spectroscopy. He was a pioneer, in
1853, to observe and study the spectrum
of hydrogen which was the foundation for
Balmer´s formula.
After leaving the observatory for the
professorship in physics at Uppsala
university (1858-1874) he continued his
spectral research.
Balmer (matematika tanár): a H-atom spektrumvonalaira
egyszerű képletet talált
1/ = const. (1/22 - 1/n2)
ahol n = 3,4,5,6
A teljesebb spektrum:
A fekete-test sugárzása
Egy példa: a kozmikus háttér spektruma egy blackbody spektrum, ahol a
hőmérséklet, TB = 2.725 K
Cosmic Microwave Background The CMB has the spectrum of a blackbody. A blackbody spectrum is
produced by an isothermal, opaque and non-reflecting object. Usually a cavity with a small hole is used in the
laboratory to make an opaque and non-reflective object. Radiation that enters the cavity through the hole will
have to bounce off many walls before it returns to the outside, so even if the walls are only somewhat dark, the
hole will appear to be completely black. The diagram at right shows such a cavity, with the blue incoming ray
being absorbed completely while the red rays show the outgoing thermal radiation. A simple gedanken
experiment shows that the spectrum emitted by a blackbody can only depend on its temperature T.
A fotoelektromos effektus
(2005: Einstein-év)
A foton energiája kvantált
E = h
Mi a rossz a rajzon?
Hiányzik a feszültségforrás
Az eredeti kísérlet picit
más volt, a kollektoron
taszító, negatív feszültség
In 1902, Lenard studied how the energy of
the emitted photoelectrons varied with the
intensity of the light. ... To measure the energy
of the ejected electrons, Lenard charged the
collector plate negatively, to repel the
electrons coming towards it. Thus, only
electrons ejected with enough kinetic energy
to get up this potential hill would contribute to
the current. Lenard discovered that there was a
well defined minimum voltage that stopped
any electrons getting through, we'll call it Vstop.
To his surprise, he found that Vstop did not
depend at all on the intensity of the light!
Doubling the light intensity doubled the
number of electrons emitted, but did not affect
the energies of the emitted electrons.
A Bohr-modell, 1913:
Heisenberg és Bohr
A Coulomb-törvény, skaláris formában:
F = kc q1q2/r2
kc = 1/(4πε) ahol ε a vakuum permittivitása.
ε = 8.854×10−12 C2N-1m-2.