Democritus (Greek) world is made up of:: empty space tiny particles (atomos) Aristotle (Greek) world is composed of continuous matter (hyle) accepted until 17 th Century
agreed with Newton and Boyle atoms were the basis (no proof) English studied Lavoisier and Proust (both were French)
Chemical change in a closed system has equal mass before and after the change, matter is neither created nor destroyed Law of Conservation of Mass
Law of Definite Proportions Specific substances always contain elements in the same ratio by mass example: H 2 O has a ratio of 1:8 (H:O)
Law of Multiple Proportions certain elements can combine to form two or more different chemical compounds Hydrogen and Oxygen can to form water (1:8) and peroxide (1:16)
All matter is composed of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. (*) Atoms cannot be subdivided, created, or destroyed. (*)
Atoms of different elements can combine in simple, whole-number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged.
These tennets are no longer true today! #2 because of isotopes #3 because of subatomic particles
~1832: FARADAY: PROPOSED EXISTANCE OF ELECTRON PROPOSED ELECTRICITY WAS CARRIED BY CHARGED ATOMS ----IONS ~1879: CROOKES: INVENTED GAS DISCHARGE TUBE (CRT) RAY FROM - “POLE” (CATHODE) TO + “POLE (ANODE) 1895: ROENTGEN: CRT HIT TARGET, GET LOWER ENERGY EMISSIONS ---- X-RAYS 1896: BEQUEREL: DISCOVERED RADIOACTIVITY! 1897: JJ THOMSON USED CRT AND EXPLORED NATURE OF THESE “RAYS”
J. J. Thomson (Eng) cathode ray tube experiment proved that the atom is divisible cathode (negative electrode) anode (positive electrode)
ZnS - + NO CHARGE ON PLATES -+-+ 1. RAY DEFLECTED BY ELECTRIC & MAGNETIC FIELD NOT LIGHT; THEREFORE, PARTICLES 2. DEFLECTION TOWARD POSITIVE PLATE PARTICLES NEGATIVELY CHARGED 3. LARGE DEFLECTION DETERMINED CHARGE/MASS (q/m) RATIO q/m < 1/1000 THE MASS OF HYDROGEN ATOM!!!!
THOMSON: “FOUND” FARADAY’S ELECTRON DETERMINED THE ATOM WAS NOT THE SMALLEST PARTICLE 1909: MILLIKEN DETERMINED THE EXACT CHARGE AND MASS OF THIS ELECTRON ALL DATA INTEGRAL VALUES OF SAME NUMBER q = -1.6 x 10 -19 C m = 9.1 x 10 -31 kg ABOUT 1/1800th OF THE HYDROGEN ATOM TODAY: 1.60219 x 10 -19 C 9.10940 x 10 -31 kg
Robert Millikan (USA) Oil Drop Experiment first to measure the mass of an electron 9.109 x 10 -28 g first to measure the charge of an electron (-1)
What is a nucleon? A nucleon is a particle that is found within the nucleus of an atom. What are the major nucleons? Proton and the Neutron
Gold Foil Experiment hit a thin piece of gold foil with a beam of alpha radiation (positively charged) some of the beam went through uninerrupted some of the beam was deflected to the side or totally reflected
1911 -- RUTHERFORD’S “GOLD FOIL” EXPERIMENT ZnS COATED SCREEN GOLD FOIL STREAM OF (ALPHA) PARTICLES 1. MOST PASS THRU UNDEFLECTED MOST OF ATOM VOLUME IS EMPTY SPACE 2. SOME POSITIVE PARTICLES DEFLECTED SLIGHTLY NEAR COLLISIONS WITH MASSIVE, POSITIVELY CHARGED PARTICLE 3. 1 OF 20000 DEFLECT ACUTELY CROSS SECTION OF MASSIVE, POSITIVELY CHARGED PARTICLE IS 1/20000 th THAT OF ATOM RUTHERFORD FOUND THE NUCLEUS!!!
Since the positively charged radiation was repelled in certain areas, there was evidence for a positive entity inside of the foil Proton This led to the idea of a central core that is very dense (nucleus) Since some of the radiation passes through unharmed the foil must not be totally positive
ATOM MUST BE A VERY DENSE, POSTIVELY CHARGED NULCLEUS SURROUNDED BY VERY LIGHT, NEGATIVELY CHARGED ELECTRONS QUANDRY: HEAVY PROTON (+ CHARGE) IN NUCLEUS LIGHT ELECTRONS ON OUTSIDE COMBINED, ACCOUNT FOR ~ 1/2 THE ATOMIC MASS AND THE ATOM IS NEUTRAL! 1932: CHADWICK ISOLATED THE NEUTRON IN NUCLEUS O CHARGE MASS ~ SAME AS PROTON
If the nucleus is the home of the majority of the mass, and the atom is electrically neutral there must be a neutral particle with a mass: neutron
Proton +1 Charge Mass:1.673 x 10 -24 g number of protons must equal the number of electrons for the atom to be neutral p+p+ Neutron No charge Mass:1.675 x 10 -24 g nono
nuclear force holds the particles together in the nucleus
Isotopes are atoms of the same element that have different masses (different numbers of neutrons).
Atomic Number ZZ number of protons Mass Number AA number of protons plus the number of neutrons
Z = protons therefore protons = 29 Protons = Electrons therefore electrons = 29 A - Z = neutrons so 65 - 29 = 36, there are 36 neutrons Now try Oxygen and Calcium:
Ions have charge due to an imbalance in the number of protons and electrons. Atoms can either gain or lose electrons. If they gain electrons the ion is negative (anion), where is they lose electrons the charge is positive (cation).
Purpose: to determine the average atomic mass of a new element called Beanium Beanium has 3 isotopes: black, black-eyed pea, and speckled bean.
If you are given a sample of Beanium, what do you need to know in order to calculate the average atomic mass. REMEMBER, that means the average mass of all three isotopes! Number of each type, mass of each type, and then total to get the average mass per atom (bean)
Type of Isotope Mass of Isotope (g) Number of Isotope Average Mass of Isotope % of Each Present Black Black- eyed pea Speckled Total100
A gaseous sample is introduced into the spectrometer and then it is bombarded by a stream of high-energy electrons. Collisions between the electrons and the sample produce cations (usually 1 + ) The positive beam passes through magnetic poles and bends, the more massive the sample the less the bend of the ray
52 MONOATOMIC CATIONS ELEMENT + ION OR ELEMENT(VALENCE) + ION Na 1+ Ca 2+ Fe 2+ Fe 3+ SODIUM IRON (II) ION IRON (III) ION CALCIUM ION Al 3+ ALUMINUM ION WHAT IS? Be 2+ Li 1+ Co 3+ Mn 5+ BERYLLIUM ION LITHIUM ION COBALT(III) ION MANGANESE(V) ION Na SODIUMION
53 ELEMENT ROOT + -IDE + ION OXYGEN IODINE OX IODIDE ION MONOATOMIC ANIONS O2-O2- I 1- WHAT IS? S 2- N 3- Br 1- Se 2- SULFIDE ION NITRIDE ION BROMIDE IONSELENIDE ION OIOI IONIDE
Higher Oxidation States for Transition metals is indicated by the –ic suffix to the Latin stem Fe 3+ is Iron (III) or ferric Lower oxidation States for Transition metals is indicated by the –ous suffix to the Latin stem Fe 2+ is Iron (II) or ferrous
Sn 4+ Sn 2+ SnCl2 FeCl3 FeCl2 Hg2 2+
56 POLYATOMIC ANIONS COVALENTLY BONDED, NON-METAL ANIONS CO 3 2- = CARBONATE IONCN 1- = CYANIDE ION OXOANIONS: CENTRAL ATOM SURROUNDED BY OXYGEN NO 3 1- NO 2 1- NITRATE ION NITRITE ION 1 LESS O ClO 1- ClO 2 1- ClO 3 1- ClO 4 1- CHLORITE ION CHLORATE ION HYPOCHLORITE ION 1 LESS O PERCHLORATE ION 1 MORE O CO 3 2- HCO 3 1- CARBONATE ION HYDROGEN CARBONATE ION
57 NAMING IONIC COMPOUNDS CATION ION + ANION ION = CATION ANION Na 1+ = SODIUM IONCl 1- = CHLORIDE ION NaCl SODIUMCHLORIDE CuBr ZnO Na 2 CO 3 Fe 2 (CO 3 ) 3 COPPER (I) BROMIDE ZINC OXIDE SODIUM CARBONATE IRON (III) CARBONATE
58 NAMING BINARY COVALENT COMPOUNDS LESS ELECTRONEGATIVE ELEMENT FIRST: EXCEPTION H RETAINS NAME MORE ELECTRONEGATIVE ELEMENT:CHANGE END TO -IDE MUST INDICATE NUMBER OF ATOMS WITH GREEK PREFIXES 1 = MONO 2 = DI 3 = TRI 4 = TETRA 5 = PENTA 6 = HEXA 7 = HEPTA 8= OCTA 9 = NONA 10 = DECA DO NOT USE MONO FOR FIRST ELEMENT DO NOT PUT TWO VOWELS TOGETHER DECAOXIDE = DECOXIDE
59 NAME THE FOLLOWING: NO N 2 O NO 2 P 2 O 5 H 2 O CF 4 P 4 O 10 NH 3 NITROGEN MONOXIDE(NITRIC OXIDE) DINITROGEN MONOXIDE NITROGEN DIOXIDE DIPHOSPHORUS PENTOXIDE TETRAPHOSPHORUS DECOXIDE DIHYDROGEN MONOXIDE(WATER) CARBON TETRAFLUORIDE NITROGEN TRIHYDRIDE(AMMONIA)
NAMING ACIDS BINARY: UNLESS DISSOLVED IN WATER -- COVALENT HBr HYDROGENHYDROBROMIDEBROMIC HYDROBROMICACID HF HI HYDROFLUORIC ACID HYDROIODIC ACID POLYATOMIC ANIONS -ITE = OUS OR -ATE = IC EXCEPTING S OR P CO 3 2- CARBONATE ION H 2 CO 3 IC ACID SO 4 2- = SULFATE ION H 2 SO 4 = SULFURIC ACID SO 3 2- = SULFITE ION H 2 SO 3 = SULFUROUS ACID
Contain Carbon and hydrogen May contain oxygen, nitrogen, sulfur, and occasionally other elements Defined by # of carbon atoms, type of bonds between the atoms, and other types of atoms bonded to the carbons
All organic compounds contain Carbon, but not all Carbon containing compounds are organic!
Family of Organic Compounds Type of Bonds between the Carbons AlkanesSingle AlkenesDouble AlkynesTriple
66 Overview Hydrocarbons: alkanes alkenes alkynes arenes
# of C 12345678910 Pre-MethEthPropButPentHexHeptOctNondec
68 R-H Functional Groups in Hydrocarbons alkanes alkenes alkynes double bond FG triple bond FG ring FG Ar-H arenes H FG
69 Functionally substituted derivatives of alkanes R-OHalcohol CH 3 CH 2 OH R-Xalkyl halideCH 3 CH 2 Cl(F,Cl,Br,I) R-DerClass Example R-NH 2 amine CH 3 CH 2 NH 2 epoxide R-O-R etherCH 3 CH 2 OCH 2 CH 3 nitrileR-C NCH 3 CH 2 C N R-NO 2 nitroalkane CH 3 CH 2 NO 2 R-SHthiolCH 3 CH 2 SH
70 Classes of cpds that contain a carbonyl group R-Der Class Example CH 3 CH 2 COHaldehyde CH 3 CH 2 COCH 3 ketone CH 3 CH 2 COOH carboxylic acid CH 3 CH 2 COOCH 3 ester
71 Methane ( CH 4 ) 4 C-H bonds All carbons are sp 3 hybridized Alkane: C n H 2n+2 Ethane ( C 2 H 6 ) 1 C-C bond 6 C-H bonds 2 C-C bond 8 C-H bonds Propane ( C 3 H 8 )
Drawn as geometric shapes where two lines meet, a carbon is indicated Lines between carbons show number of bonds between carbon Naming: use prefix cyclo-, then name according to normal organic system