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Chemistry - science studying the properties and behavior of matter Matter - physical material of the universe - anything that has mass and occupies space States of matter: 1) gas (no fixed volume or shape) 2) liquid (distinct volume but no specific shape) 3) solid (both definite shape and volume) Pure substance – matter that has fixed composition and distinct properties (sodium chloride, water) 2 categories of substances: Elements – cannot be decomposed by chemical methods into simpler substances (carbon, oxygen, iron) = consist of one kind of atoms Compounds – contain two or more kinds of atoms (water – H2O sodium chloride NaCl) Structure of the atom atom – the smallest particle of an element having its chemical properties ("atomos" in old Greek language = "indivisible") 3 types of subatomic (elementary) particles: PROTONS NEUTRONS ELECTRONS "nucleons" Particle Symbol Relative charge Relative mass Proton p positive +1 1 Neutron n 0 1 Electron e negative -1 negligible * relative mass – expressed in „atomic mass units“ (relative atomic mass, relative molecular mass) atomic mass unit = 1/12 of the mass of an atom of the carbon isotope 12C (1.66 x 10-24 g) * mass of the electron = only 1/1836 of the mass of the proton Atoms have no overall charge ==> number of protons = number of electrons This number is different for every element ! = ATOMIC number ( Z ) Element = mixture of atoms with the same number of protons (the atomic number) The chemical properties of any given element are determined by the arrangement of electrons around the nucleus. Every atom is characterized by 2 numbers: Atomic number (Z) = number of protons - it determines the element = symbol: C, N, Fe Mass (nucleon) number (A) = number of nucleons (protons + neutrons) mass number atomic number 12 6 C symbol of element Nuclide - specific atomic number Z and mass number A for example: 12 6C 238 92 U - most elements are mixtures of different nuclides ! (same atomic number, different mass numbers) = same number of protons, variation in number of neutrons = ISOTOPES of an element ------------------------------------------------------------------Term "nuclide" - more general - used: only one nucleus or several nuclei of different elements Term "isotope" - used when referring to several different nuclides of the same element Isotopes of hydrogen neutrons proton 1 1 2 1 H hydrogen 3 1 H deuterium (D) H tritium (T) The isotopes of an element have a different number of NEUTRONS -identical chemical properties water H2O "heavy water" D2O Isotopes of carbon 12 6 13 6 C 14 6 C C ------------------------------------------------------------------------------------------------ Certain isotopes of some elements are radioactive ! Radioactive decay = unstable atomic nucleus "loses energy" by emitting: particle a = 4 2 particle b = 0 -1 g 14 6 C half life 5730 years 14 7 N + He e rays ( = high-energy photon) 0 -1 e + antineutrino Electrons - surround the nucleus in energy levels (shells, orbits) 1 electron 6 electrons 15 electrons The chemical reactions = interaction of electrons from the OUTERMOST orbit Arrangement of electrons in the atom 4 quantum numbers: 1) n principle quantum number - determines energy level - positive integral values 1, 2, 3, 4, ... K, L, M, N, ... 2) l orbital quantum number - determines the shape of electron cloud - values from 0 to (n-1) 0, 1, 2, 3, ... s p d f 3) m magnetic quantum number - determines orientation of electron cloud in space - integral values from –l to +l 4) s spin - determines the intrinsic state of an electron - only 2 possible values: +½ or -½ The s orbitals orbital quantum number l=0 magnetic quantum number m = 0 (only possib.) in each s orbital can be only 2 electrons (with different SPIN) 1s 1s1 1s 1s2 "spherical" The p orbitals "two lobes" orbital quantum number magnetic quantum number l=1 m = -1 0 1 in each p orbitals can be 2 x 3 = 6 electrons 2p 2p2 2p 2p6 The d orbitals orbital quantum number magnetic quantum number l=2 m = -2 -1 0 1 2 in each d orbitals can be 2 x 5 = 10 electrons 3d 3d7 Rules that must be respected 1) The lowest "energy levels" are occupied first. 2) Hund‘s rule: No electron pairing in p, d, f orbitals until each orbital of given set contains one electron. 3) Pauli exclusion principle: No TWO electrons in any given atom can have exactly the same set of all 4 quantum numbers. Electron configuration of several elements Electrons Orbital diagram 1s2 2s1 1s2 2s2 1s2 2s2 2p1 1s2 2s2 2p2 1s2 2s2 2p3 1s2 2s2 2p6 1s2 2s2 2p6 3s1 The periodic properties of the elements The elements with similar arrangement (configuration) of electrons in the outer (superficial) shell have SIMILAR CHEMICAL PROPERTIES Periodic table Dmitri Mendeleyev (1869) - Russian chemist - elements are listed in order of increasing atomic number horizontal rows = PERIODS vertical columns = GROUPS elements in groups: the same number of electrons in outermost orbits = similar chemical properties Names for some of the groups Group Name Elements IA Alkali metals Li, Na, K, Rb, Cs, Fr II A Alkaline earth metals Be, Mg, Ca, Sr, Ba, Ra VI A Chalcogens O, S, Se, Te, Po VII A Halogens F, Cl, Br, I Noble (rare, inert) gases He, Ne, Ar, Kr, Xe, Rn VIII A (0) Chemical bonding Covalent bond - sharing of one or more pairs of electrons Coordinate covalent bond - both electrons of the bond belong to one atom, the other has empty orbital Ionic bond - big difference of electronegativities - IONS attracted by electrostatic forces Na+ Cl- Hydrogen bonding a weak electrostatic interaction between partly (+) charged hydrogen atom and partly (-) charged another atom (O, N, F) R N R H bonds (+) (-) H ............. O R C vodíkový můstek R important in stabilizing the structures of: PROTEINS NUCLEIC ACIDS The EARTH Core (inner, outer) Mantle Crust Crust Lithosphere Hydrosphere Atmosphere Biosphere 93 % 7% 0.03 % 0.001 % The elementary composition (%) Earth crust Human body O 49.5 62.4 Si 25.7 - Al 7.5 - Fe 4.7 0.005 H 0.9 9.8 P 0.12 1.0 C 0.09 21.1 S 0.06 0.16 N 0.03 3.1 - elementary composition of the human body is very different from that of lithosphere Specific selection of some elements for the biological uses % in human body % in the Earth crust C 243 N 103 H 11 P 8 S 2.7 O 1.26 Fe 0.001 Al 0.000 13 Si 0.000 04 - some chemical elements (C, H, N, O, ...) are "better" than others to make up molecules of living organisms - most abundant elements of the Earth core: Fe, Ni - most abundant elements of the Earth crust: O, Si, Al, Fe - most abundant elements in living organisms: O, C, H, N - oxygen is the most abundant element both on the Earth surface and in human body The atmosphere of the Earth Composition of the AIR Water vapour 1-4% The dry air (by volume) Nitrogen Oxygen Argon Carbon dioxide All others 78 % 21 % 0.93 % 0.038 % only trace amounts The geological development of the atmosphere • the loss of very light gases ( H2 • the increase of O2 20th centrury - slight increase of CO2 burning of coal, gas, oil destruction of forests and phytoplankton current levels 0.0296 % 0.0385 % CH4 ) (photolysis of water by the green plants) • fixation of CO2 by photosynthesis 1900 He 296 ppm 385 ppm The greenhouse effect CO2 is a "greenhouse gas" - global warming The oxygen cycle O2 Animals, plants RESPIRATION CO2 H2O We need per day: air water food Plants PHOTOLYSIS of H2O PHOTOSYNTHESIS 15 000 l [ 13.5 kg ] 2 kg 1.2 kg Comparison of inspired and expired air Inspired Expired O2 21 % 15 % CO2 0.03 % 5% N2 78 % 78 % CO2 is a waste product of respiration Air pollution Emissions = the pollutants released into the environment Pollution natural industrial Natural sources Volcano eruptions Dust storms Fires Lightnings Biological decomposition dust dust dust NO CO2 ash SO2 ash CO2 CO NO2 H2S NH3 CH4 Dust particles water condensation CLOUDS, RAIN Impact of big meteor heavy dust pollution of atmosphere climate changes ( extinction of giant reptiles in mesozoic era ? ) Industrial sources The progress of civilization global air pollution (overcharging of the natural cycles of regeneration and detoxication) 1) 2) 3) 4) 5) 6) dust – ashes Sulphur dioxide ( SO2 ) Nitrogen oxides ( NOx ) Carbon oxides ( CO2 CO ) Toxic metals Organic compounds Particulate matter - dust, ashes complex mixture of extremely small particles and liquid droplets sources: power plants, industrial and agriculture processes, transport, home effects: irritation of respiratory system contains adsorbed number of components: toxic metals, SO2 cancerogenic hydrocarbons the size of particles is directly linked to their potential for causing health problems - smaller than 10 mm pass through the airways and enter the lung ! SMOG [ smoke + fog ] "London smog" HELP: industry, power plants - electrostatic precipitation home - no burning of coal and peat - using gas or oil, solar energy Sulphur dioxide SO2 main source: burning of soft coal ( 1 % S as sulphides of Fe ) Europe 1980: 40 000 000 tons of SO2 ( ¾ bound to fly ash ) irritation of respiratory system, rhinitis, laryngitis SO2 + H2O H2SO3 SO2 SO3 + H2O H2SO4 sulphurous acid (weak acid) sulphuric acid (strong acid) ACID RAIN pH ~ 4 acidification of soil solution of minerals Al3+ Pb2+ Cu2+ ... intoxication of plants and animals green plants: CO2 x SO2 competition destruction of photosynthetic enzymes (damage of pine forests) Sulphur dioxide SO2 HELP: Power plants: soft coal + CaCO3 CaSO4 ("gypsum") OR SO2 + Ca(OH)2 CaSO4 Acid soil: + CaCO3 + Ca(OH)2 ("limestone") ("lime water") Nitrogen oxides NO NOx limit: 0.1 mg / m3 NO2 brown haze sources: motor vehicles, power plants, chemical industry secondary pollutants: OZONE ( O3 ) PAN = peroxyacylnitrates sun light NO2 NO + O Photochemical smog ( "Los Angeles – type" smog ) O2 + O O3 O3 + hydrocarbons aldehydes (car exhausts) + NO2 PAN very irritating to eyes and respiratory system "London – type" smog combustion of coal = smoke + fog emission of sulphur dioxide ( SO2 ) and dust + mixed with FOG "Los Angeles – type" smog dry air + sunny days + NOx + volatile organic gases (emitted by automobiles) = photochemical smog Carbon dioxide CO2 colorless, odorless gas "overproduction" sources: burning of fossil fuels air: 0.038 % higher levels stimulate breathing long time respiration of 5 % CO2 respiration troubles > 15 % DEATH Danger: old mines, caves, wine cellars (heavier than air it tends to go down) Carbon monoxide CO colorless, odorless gas sources: car exhausts, incomplete burning (smouldering) local street pollution – dangerous level: 10 ppm / 8 hours TOXIC: very high affinity to HEMOGLOBIN 35 ppm / 1 hour carbonylhemoglobin impaired ability of the blood to transport O2 oxygen deprivation drowsiness unconsciousness DEATH Toxic heavy metals Lead Pb - tetraethyllead was used as antiknock agent in gasoline (organometallic compound) Pb (CH2CH3)4 neurotoxic PbO (lead oxide aerosol) deposition in the vicinity of highways toxic effects of inorganic lead compounds: impaired heme synthesis anemia Toxic metals aerosol As, Pb, Cd, Hg, ... oxides bound to ash particulate matter - source: power plants ( COAL ! ), smelters - general toxicity – decrease of vitality Organic compounds Hydrocarbons – motor vehicles, industry, cigarette smoke ( TAR ) - carcinogens, precursors to PAN Freons - hydrocarbons with hydrogen atoms substituated by F, Cl = chlorofluorocarbons ( CFCs ) - in older refrigeration and air-conditioning systems - effect: destroying the ozone layer in the stratosphere Indoor air pollution Respiration CO2 ( H2O) Digestion (intestinal bacteria) H2S Gas stove CO2 CO indole ( H2O) Tobacco smoke TAR (cancerogens) Formaldehyde Radon Rn HCHO nicotine - released from foamed insulation tapestry plywood adhesives - radioactive gas - radon from natural sources can accumulate in buildings 222 86 Rn 4 2 He + 218 84 Po Water non-bonding electron pairs O H2O H 105o H bent molecule d- polar character O H d+ - H + d+ electrical dipole Hydrogen bonding - attractions between water molecules + + + - + - + 0 oC 3.6 / H2O HIGH melting point boiling point specific heat heat of vaporization surface tension H bonds - much weaker than covalent bonds ! bond energy of H-bonds in liquid water: about 19 kJ/mol ( covalent H – O bond in water: 460 kJ/mol ) water is most dense at 3.98 °C !!! (when freezing, ice will form first on the surface) WATER - very good solvent ! Attraction between water dipoles and ions "hydrated ions" Dispersing "amphipathic" molecules "micelles" "Amphipathic" molecules – contain both highly hydrophobic and highly polar groups palmitic acid non-polar chain = hydrophobic polar group = hydrophilic (water-fearing) (water-loving) Phospholipids phosphatidylcholine (lecithin) polar groups Water in human body ~ 60 % of the body weight intracellular ~ 40 % extracellular ~ 20 % PLASMA 5% interstitial fluid 15 % - a very complex solution of inorganic & organic components Phosphates Proteins K+ Na+ Mg2+ Na+ Cl- Na+ K+ Ca2+ HCO3- Mg2+ Phosphates K+ Na+/K+ pump ( = Na+/K+ -ATPase ) Blood plasma ( extracellular fluid ) Cell fluid (cytosol) ( intracellular fluid ) Human blood plasma mmol/l Na+ 132 – 145 K+ 3.8 - 5.2 Ca* 2.1 – 2.6 Mg2+ 0.8 – 1.1 Cl- 97 – 108 HCO3- 22 – 26 Phosphates HPO42- + H2PO4- 0.6 – 1.6 pH = 7.36 – 7.44 * Ca "total Ca" Ca2+ "ionized" is about ½ of "total" ~ 1.2 mmol/l Colligative properties of solutions - dependent on the number of solute particles the same effect Effects of a solute on a solvent: depression of the freezing point elevation of the boiling point depression of the vapour pressure osmotic pressure osmolality = moles of solute particles dissolved in 1 kg of solvent ( osmolality of blood plasma: 285 mmol/kg ) Water balance Intake: ~ 1.5 - 2.0 l / day metabolic water (produced in human body by oxidation of food) 0.3 – 0.5 l /day Resorption: stomach, small intestine, LARGE INTESTINE Secretion: Excretion: Saliva Stomach Bile Pancreas Small intestine 1 500 ml / day 2 500 500 700 3 000 Urine 60 % Skin 20 % (perspiration) Lungs 15 % Faeces 5 % 8 200 ml /day Water in nature Hardness of water: technical problems – deposits after boiling Temporary hardness: cause = Ca(HCO3)2 Boiling: Ca(HCO3)2 soluble in water CaCO3 + CO2 + H2O Softening water in water stations: Ca(HCO3)2 + Ca(OH)2 2 CaCO3 + 2 H2O Permanent hardness: cause = CaCl2 CaSO4 ... softening: CaSO4 + Na2CO3 CaCO3 + Na2SO4 Biological pollution of water urine, excrements, dead bodies BACTERIAL decomposition (most efficiently by aerobic bacteria) I. organic compounds: UREA, proteins, peptides II. NH3 III. NO2- markers of RECENT pollution ammonia NO3- - final decomposition products - good for plant nutrition EUTROPHICATION of water - fertilizers, phosphates (compounds of N, P) The bioelements (summary) 1) Principal bioelements: O, C, N, H, P, S (biomolecules: proteins, nucleic acids, lipids, saccharides) 2) Water and ions ( H2O ) Na+, K+, Mg2+, Ca2+, Cl-, ( HCO3- , phosphates) 3) Mineral constituents of bones and teeth Ca (Mg, Na) PO43- CO32- ( F- Cl- ) 4) Microelements (trace elements) Fe, Cu, Co, Zn, I, F, Se, ... -------------------------------------------------------- 5) Contamination (intoxication): Hg, Al, ...