Atoms, Molecules, and Atoms, Molecules, and IonsIons
Chemistry Timeline #1Chemistry Timeline #1B.C.400 B.C. Demokritos and Leucippos use the term "atomos”
1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals
1600'sRobert Boyle:The Skeptical Chemist. Quantitative experimentation, identification of elements
1700s'Georg Stahl: Phlogiston TheoryJoseph Priestly: Discovery of oxygen Antoine Lavoisier: The role of oxygen in combustion, law of conservation of mass, first modern chemistry textbook
2000 years of Alchemy
Chemistry Timeline #2Chemistry Timeline #2
1800'sJoseph Proust: The law of definite proportion (composition) John Dalton: The Atomic Theory, The law of multiple proportionsJoseph Gay-Lussac: Combining volumes of gases, existence of diatomic moleculesAmadeo Avogadro: Molar volumes of gasesJons Jakob Berzelius: Relative atomic masses, modern symbols for the elements Dmitri Mendeleyev: The periodic table J.J. Thomson: discovery of the electron Henri Becquerel: Discovery of radioactivity
1900's Robert Millikan: Charge and mass of the electron Ernest Rutherford: Existence of the nucleus, and its relative size Meitner & Fermi: Sustained nuclear fission Ernest Lawrence: The cyclotron and trans-uranium elements
Dalton’s Atomic Theory Dalton’s Atomic Theory (1808)(1808)
Atoms cannot be subdivided, created, or destroyed Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined, separated, or rearranged
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
John Dalton
Modern Atomic TheoryModern Atomic TheorySeveral changes have been made to Dalton’s theory.
Dalton said:
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties
Modern theory states:Atoms of an element have a
characteristic average mass which is unique to that element.
Modern Atomic Theory #2Modern Atomic Theory #2
Dalton said:
Modern theory states:
Atoms cannot be subdivided, created, or destroyed
Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions!
Discovery of the ElectronDiscovery of the ElectronIn 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle.
Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.
Thomson’s Atomic Thomson’s Atomic ModelModel
Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.
Mass of the ElectronMass of the Electron
1909 – Robert Millikan determines the mass of the electron.
The oil drop apparatus Mass of the
electron is 9.109 x 10-31 kg
Conclusions from the Study Conclusions from the Study of the Electronof the Electron
Cathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons.Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons Electrons have so little mass that atoms must contain other particles that account for most of the mass
Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment
Alpha particles are helium nuclei Particles were fired at a thin sheet of gold foil Particle hits on the detecting screen (film) are recorded
Try it Yourself!Try it Yourself!In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?
The AnswersThe Answers
Target #1 Target #2
Rutherford’s FindingsRutherford’s Findings
The nucleus is small The nucleus is dense The nucleus is positively charged
Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflected
“Like howitzer shells bouncing off of tissue paper!”
Conclusions:
Atomic ParticlesAtomic ParticlesParticle Charge Mass (kg) Location
Electron
-1 9.109 x 10-31 Electron cloud
Proton +1 1.673 x 10-27 Nucleus
Neutron
0 1.675 x 10-27 Nucleus
The Atomic The Atomic ScaleScale
Most of the mass of the atom is in the nucleus (protons and neutrons) Electrons are found outside of the nucleus (the electron cloud) Most of the volume of the atom is empty space
“q” is a particle called a “quark”
About Quarks…About Quarks…Protons and neutrons are NOT fundamental particles.Protons are made of two “up” quarks and one “down” quark.Neutrons are made of one “up” quark and two “down” quarks.
Quarks are held togetherby “gluons”
IsotopesIsotopesIsotopes are atoms of the same element having different masses due to varying numbers of neutrons.Isotope Proto
nsElectron
sNeutron
sNucleus
Hydrogen–1
(protium)
1 1 0
Hydrogen-2
(deuterium)
1 1 1
Hydrogen-3
(tritium)
1 1 2
Atomic Atomic MassesMasses
Isotope Symbol Composition of the nucleus
% in nature
Carbon-12
12C 6 protons6 neutrons
98.89%
Carbon-13
13C 6 protons7 neutrons
1.11%
Carbon-14
14C 6 protons8 neutrons
<0.01%
Atomic mass is the average of all the naturally isotopes of that element.Carbon = 12.011
Atomic NumberAtomic NumberAtomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.
Element # of protons Atomic # (Z)
Carbon 6 6
Phosphorus 15 15
Gold 79 79
Mass NumberMass NumberMass number is the number of protons and neutrons in the nucleus of an isotope.Mass # = p+ + n0
Nuclide p+ n0 e- Mass #
Oxygen - 10
- 33 42
- 31 15
8 8 1818
Arsenic 75 33 75
Phosphorus 15 3116
MoleculesMolecules
Two or more atoms of the same or different elements, covalently bonded together.
Molecules are discrete structures, and their formulas represent each atom present in the molecule.
Benzene, C6H6
Covalent Network Covalent Network SubstancesSubstances
Covalent network substances have covalently bonded atoms, but do not have discrete formulas.
Why Not??
Graphite Diamond
IonsIonsIonsIons CationCation: A positive ion: A positive ion
• MgMg2+2+, NH, NH44++
AnionAnion: A negative ion: A negative ion ClCl, SO, SO44
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Ionic BondingIonic Bonding: Force of attraction : Force of attraction between oppositely charged ions.between oppositely charged ions.
Ionic compounds form Ionic compounds form crystalscrystals, so their , so their formulas are written formulas are written empirically empirically (lowest (lowest whole number ratio of ions).whole number ratio of ions).
Periodic Table with Group Names
Easily lose valence electron (Reducing agents)
React violently with water Large hydration energy React with halogens to form
salts
The Properties of a Group: the Alkali Metals
Predicting Ionic ChargesPredicting Ionic Charges
Group 1Group 1::Lose 1 electron to form Lose 1 electron to form 1+1+ ions ions
HH++ LiLi++ NaNa++ KK++
Predicting Ionic ChargesPredicting Ionic Charges
Group 2Group 2::Loses 2 electrons to form Loses 2 electrons to form 2+2+ ions ions
BeBe2+2+ MgMg2+2+ CaCa2+2+ SrSr2+2+ BaBa2+2+
Predicting Ionic ChargesPredicting Ionic ChargesGroup 13Group 13:: Loses 3 Loses 3 electrons to form electrons to form 3+3+ ions ions
BB3+3+ AlAl3+3+ GaGa3+3+
Predicting Ionic ChargesPredicting Ionic ChargesGroup 14Group 14:: Loses 4 Loses 4 electrons or electrons or gains gains 4 electrons4 electrons
Caution! Caution! CC222-2- and C and C4-4-
are both called are both called carbidecarbide
Predicting Ionic ChargesPredicting Ionic ChargesGroup 15Group 15:: Gains 3 Gains 3 electrons to form electrons to form 3-3- ions ions
NN3-3-
PP3-3-
AsAs3-3-
Nitride
Phosphide
Arsenide
Predicting Ionic ChargesPredicting Ionic ChargesGroup 16Group 16:: Gains 2 Gains 2 electrons to form electrons to form 2-2- ions ions
OO2-2-
SS2-2-
SeSe2-2-
Oxide
Sulfide
Selenide
Predicting Ionic ChargesPredicting Ionic ChargesGroup 17Group 17:: Gains 1 Gains 1 electron to form electron to form 1-1- ions ions
FF1-1-
ClCl1-1-
BrBr1-1-Fluoride
Chloride
Bromide
II1-1- Iodide
Predicting Ionic ChargesPredicting Ionic ChargesGroup 18Group 18:: Stable Stable Noble gases Noble gases do do notnot form ions! form ions!
Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 - Groups 3 - 1212::
Many Many transitiontransition elements elements have more than one possible oxidation have more than one possible oxidation state.state.Iron(II) = Fe2+ Iron(III) = Fe3+
Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 - Groups 3 - 1212::
Some Some transitiontransition elements elements have only one possible oxidation state.have only one possible oxidation state.
Zinc = Zn2+ Silver = Ag+
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Barium nitrate
1. Write the formulas for the cation and anion, including CHARGES!
BaBa2+2+ NONO33--2. Check to see if charges are
balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced!
( )( ) 22
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Ammonium sulfate
1. Write the formulas for the cation and anion, including CHARGES!
NHNH44++ SOSO44
2-2-2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced!
( )( )22
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion, including CHARGES!
FeFe3+3+ClCl--2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced!
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Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion, including CHARGES!
AlAl3+3+ SS2-2-2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced!
22 33
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Magnesium carbonate
1. Write the formulas for the cation and anion, including CHARGES!
MgMg2+2+ COCO332-2-2. Check to see if
charges are balanced.
They are balanced!
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Zinc hydroxide
1. Write the formulas for the cation and anion, including CHARGES!
ZnZn2+2+ OHOH--2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced!
( )( )22
Writing Ionic Compound Writing Ionic Compound FormulasFormulas
Example: Aluminum phosphate
1. Write the formulas for the cation and anion, including CHARGES!
AlAl3+3+ POPO443-3-2. Check to see if charges are
balanced.
They ARE balanced!
Naming Ionic CompoundsNaming Ionic CompoundsNaming Ionic CompoundsNaming Ionic Compounds• 1. Cation first, then anion1. Cation first, then anion
• 2. Monatomic cation = name of the 2. Monatomic cation = name of the elementelement
• CaCa2+2+ = calcium = calcium ionion
• 3. Monatomic anion = 3. Monatomic anion = rootroot + + -ide-ide• ClCl = chlor = chlorideide
• CaClCaCl22 = calcium chlor= calcium chlorideide
Naming Ionic CompoundsNaming Ionic Compounds(continued)(continued)
Naming Ionic CompoundsNaming Ionic Compounds(continued)(continued)
some some metal forms more than one metal forms more than one cationcation use use Roman numeralRoman numeral in namein name
PbClPbCl22
PbPb2+2+ is the lead(is the lead(IIII) cation) cation
PbClPbCl22 = lead( = lead(IIII) chloride) chloride
Metals with multiple oxidation Metals with multiple oxidation statesstates
Naming Binary CompoundsNaming Binary CompoundsNaming Binary CompoundsNaming Binary Compounds Compounds between two Compounds between two nonmetalsnonmetals First element First element in the formula is in the formula is named firstnamed first.. Second element Second element is named as if it were an is named as if it were an
anionanion.. Use prefixesUse prefixes Only use Only use monomono on second element - on second element -
PP22OO55 ==COCO22 = =
CO =CO =
NN22O =O =
didiphosphorus phosphorus pentpentoxideoxide
carbon carbon didioxideoxide
carbon carbon monmonoxideoxide
didinitrogen nitrogen monmonoxideoxide