Atoms, Molecules & Ions
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Transcript of Atoms, Molecules & Ions
ATOMS, MOLECULES & IONS
A Review of Early Atomic Models, Periodic Table Development, and Nomenclature
Early Atomic Models
Early History Democritus (Greek)
world is made up of:: empty space tiny particles (atomos)
Aristotle (Greek) world is composed of continuous matter
(hyle) accepted until 17th Century
John Dalton agreed with Newton
and Boyle atoms were the basis
(no proof) English studied Lavoisier
and Proust (both were French)
Lavoisier 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
Proust Law of Definite Proportions Specific substances always contain
elements in the same ratio by mass example: H2O has a ratio of 1:8
(H:O)
Dalton’s Law 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)
Dalton’s Atomic Theory 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. (*)
Atomic Theory con’t Atoms of different elements can
combine in simple, whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged.
What does the * mean?
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”
Subatomic Particles: Electron
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 FIELDNOT LIGHT; THEREFORE, PARTICLES
2. DEFLECTION TOWARD POSITIVE PLATEPARTICLES NEGATIVELY CHARGED
3. LARGE DEFLECTIONDETERMINED 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 Cm = 9.1 x 10-31 kg
ABOUT 1/1800th OF THE HYDROGEN ATOM
TODAY: 1.60219 x 10-19 C9.10940 x 10-31 kg
Thomson’s Model: Plum Pudding
+
++
Subatomic Particles: Electron Robert Millikan (USA)
Oil Drop Experiment first to measure
the mass of an electron 9.109 x 10-28g
first to measure the charge of an electron (-1)
Subatomic Particles: The Nucleons 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
Ernest Rutherford (New Zealand)
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” EXPERIMENTZnS COATED
SCREEN
GOLDFOIL
STREAM OF a (ALPHA)
PARTICLES
1. MOST PASS THRU UNDEFLECTEDMOST OF ATOM VOLUME IS
EMPTY SPACE
2. SOME POSITIVE a PARTICLES DEFLECTED SLIGHTLY
NEAR COLLISIONS WITH MASSIVE, POSITIVELY CHARGED PARTICLE
3. 1 OF 20000 DEFLECT ACUTELYCROSS SECTION OF MASSIVE, POSITIVELY CHARGED PARTICLE IS 1/20000th THAT OF ATOM
RUTHERFORD FOUND THE NUCLEUS!!!
Rutherford’s Results 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 CHARGEDNULCLEUS SURROUNDED BY VERY LIGHT, NEGATIVELY
CHARGED ELECTRONS
QUANDRY:HEAVY PROTON (+ CHARGE) IN NUCLEUSLIGHT ELECTRONS ON OUTSIDE
COMBINED, ACCOUNT FOR ~ 1/2 THE ATOMIC MASSAND THE ATOM IS NEUTRAL!
1932: CHADWICK ISOLATED THE NEUTRON
IN NUCLEUSO CHARGEMASS ~ SAME AS PROTON
Chadwick 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
Comparison of the Major Nucleons Proton
+1 Charge Mass:1.673 x 10-
24g number of protons
must equal the number of electrons for the atom to be neutral
p+
Neutron No charge Mass:1.675 x 10-
24g no
What holds it all together?
nuclear force holds the particles together in the nucleus
What are isotopes? Isotopes are atoms of the same
element that have different masses (different numbers of neutrons).
What do the numbers mean? Atomic Number
Z number of protons
Mass Number A number of protons
plus the number of neutrons
Where do you find the numbers?
Using the periodic table locate the symbol for the element that you are looking for. Inside the element’s square will be the numbers.
Writing Nuclides
XCopperOxygenSilver
The Isotopes of HydrogenName of Isotope Atomic # Mass # no
Protium 1 1 0Deuterium 1 2 1
Tritium 1 3 2
The Isotopes of Hydrogen
How many electrons, protons, and neutrons are found in a copper atom of mass # 65? 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 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).
Try these: O 2-
Ca 2+
Isotopes of Beanium Lab 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)
Data Table for Beanium Lab
Type of Isotope
Mass of Isotope
(g)
Number of
Isotope
Average Mass of Isotope
% of Each
PresentBlack
Black-eyed peaSpeckled
Total 100
Mass Spectrometer 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
A full diagram of a mass spectrometer
THE PERIODIC TABLE
Families of the Periodic Table
Column # Family Name Valence e- Oxidation #
1 Alkali Metals 1 1+
2 Alkaline Earth Metals
2 2+
3 Boron Family 3 3+/5-
4 Carbon Family 4 4+/4-
5 Nitrogen Family 5 3-
6 Chalcogens 6 2-
7 Halogens 7 1-
8 Noble Gases 8 0
Metals Loose electrons (oxidation) to form ions
that are positively charged (cations) Good conductors (allow energy to flow
through them) of heat and electricity Have 3 or less valence electrons
Non-metals Gain electrons (reduction) in order to
form negatively charged ions (anions) Good insulators (don’t allow heat or
electricity to flow through them) 4 or more valence electrons
Metalloids Found on the periodic table along the
“staircase” Have properties of both metals and
non-metals depending upon the particular situation
Also called the semi-metals
Molecules
Molecules An assembly of two or more atoms
tightly bound together Represented by a chemical formula
(written as a collection of element symbols and subscripts to indicate the # of each element)
Monatomic vs. Diatomic Some elements exist in nature as pairs
of atoms: diatomic “H and the 7” N O F
Br Cl I
Empirical Formula Simplest, true formula of a compound C2H8 can be simplified to CH4
Molecular Formula The TRUE formula for the ratio of
elements in a compound
Inorganic Nomenclature
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HELLO……MY NAME IS
NAMING IONS
AND COMPOUNDS
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MONOATOMIC CATIONS
ELEMENT + ION OR ELEMENT(VALENCE) + ION
Na1+ Ca2+
Fe2+
Fe3+
SODIUM
IRON (II) ION
IRON (III) ION
CALCIUM ION
Al3+ ALUMINUM ION
WHAT IS?
Be2+ Li1+
Co3+ Mn5+
BERYLLIUM ION LITHIUM ION
COBALT(III) ION MANGANESE(V) ION
Na SODIUM ION
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ELEMENT ROOT + -IDE + ION
OXYGEN
IODINE
OX
IODIDE ION
MONOATOMIC ANIONS
O2-
I1-
WHAT IS?
S2- N3-
Br1- Se2-
SULFIDE ION NITRIDE ION
BROMIDE ION SELENIDE ION
OI
IONIDE
Suffix Naming System Higher Oxidation States for Transition
metals is indicated by the –ic suffix to the Latin stem Fe3+ is Iron (III) or ferric
Lower oxidation States for Transition metals is indicated by the –ous suffix to the Latin stem Fe2+ is Iron (II) or ferrous
Name these: Sn4+
Sn2+
SnCl2 FeCl3 FeCl2 Hg22+
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POLYATOMIC ANIONS
COVALENTLY BONDED, NON-METAL ANIONS
CO32- = CARBONATE ION CN1- = CYANIDE ION
OXOANIONS: CENTRAL ATOM SURROUNDED BY OXYGEN
NO31-
NO21-
NITRATE IONNITRITE ION
1 LESS O
ClO1-
ClO21-
ClO31-
ClO41-
CHLORITE IONCHLORATE ION
HYPOCHLORITE ION
1 LESS O
PERCHLORATE ION
1 MORE OCO32-
HCO31-
CARBONATE IONHYDROGEN CARBONATE ION
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NAMING IONIC COMPOUNDS
CATION ION + ANION ION = CATION ANION
Na1+ = SODIUM ION Cl1- = CHLORIDE ION
Na Cl
SODIUM CHLORIDE
CuBr
ZnO
Na2CO3
Fe2 (CO3) 3
COPPER (I) BROMIDE
ZINC OXIDE
SODIUM CARBONATE
IRON (III) CARBONATE
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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 PREFIXES1 = MONO2 = DI3 = TRI4 = TETRA5 = PENTA
6 = HEXA7 = HEPTA8= OCTA9 = NONA10 = DECA
DO NOT USE MONO FOR FIRST ELEMENTDO NOT PUT TWO VOWELS TOGETHER
DECAOXIDE = DECOXIDE
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NAME THE FOLLOWING:
NO
N2O
NO2
P2O5
H2O
CF4
P4O10
NH3
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
HYDROGENHYDRO BROMIDEBROMICHYDROBROMIC ACID
HFHI
HYDROFLUORIC ACIDHYDROIODIC ACID
POLYATOMICANIONS
-ITE = OUS OR -ATE = ICEXCEPTING S OR P
CO3 2- CARBON ATE IONH2 CO3 IC ACID
SO42- = SULFATE ION H2 SO4 = SULFURIC ACID
SO32- = SULFITE ION H2 SO3 = SULFUROUS ACID
Name these: HBr H2S H2SO4 H2SO3 HNO3 HN
Organic Nomenclature
Organic compounds 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!
Types of Organic CompoundsFamily of Organic Compounds
Type of Bonds between the Carbons
Alkanes SingleAlkenes DoubleAlkynes Triple
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OverviewHydrocarbons:
•alkanes•alkenes•alkynes•arenes
Prefixes Indicating the # of Carbons present
# of C
1 2 3 4 5 6 7 8 9 10
Pre-
Meth
Eth
Prop
But Pent
Hex
Hept
Oct
Non
dec
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R-H
Functional Groups in Hydrocarbons
•alkanes•alkenes•alkynes double bond
FG
triple bondFG
ringFG
Ar-H•arenes
arenes
HFG
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Functionally substituted derivativesof alkanes
R-OH alcohol CH3CH2OH
R-X alkyl halide CH3CH2Cl (F,Cl,Br,I)
R-Der Class Example
R-NH2 amine CH3CH2NH2
R2C CR2
Oepoxide
H2C CH2
OR-O-R ether CH3CH2OCH2CH3
nitrileR-C N CH3CH2C N
R-NO2 nitroalkane CH3CH2NO2
R-SH thiol CH3CH2SH
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Classes of cpds that contain a carbonyl group
R-Der Class Example
O
C
CH3CH2COHO
CHRaldehyde
CH3CH2COCH3
O
CRRketone
CH3CH2COOHO
COHR
carboxylicacid
O
CH
O
C
O
CO
H
O
CO
CH3CH2COOCH3
O
CORRester
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Methane (CH4)
H
HC
HH 4 C-H s bonds
All carbons are sp3 hybridizedAlkane: CnH2n+2
H
CC
H H
HH
HEthane (C2H6)
1 C-C s bond
6 C-H s bonds
H CC
H
C
HH
H
H
HH
2 C-C s bond
8 C-H s bondsPropane (C3H8)
Name these compounds CH4
C2H6
C5H12
C10H22
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CH4
CH3 CH3
methane
Alkane Nomenclature (IUPAC rules)
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane
Unbranched Alkanes
Cyclic Hydrocarbons 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
Name these:
The Special ring
Benzene(C6H6)
What’s so special about Benzene?
Congratulations we’re finally done with this unit!