atoms, molecules, and ions. chemistry timeline #1 b.c. 400 b.c. demokritos and leucippos use the...

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


1.11%

Carbon-14


<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

22

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


Example: Ammonium sulfate


NHNH44++ SOSO44

2-2-2. Check to see if charges are balanced.


Not balanced!

( )( )22


Example: Iron(III) chloride


FeFe3+3+ClCl--2. Check to see if charges are balanced.


Not balanced!

33


Example: Aluminum sulfide


AlAl3+3+ SS2-2-2. Check to see if charges are balanced.


Not balanced!

22 33


Example: Magnesium carbonate


MgMg2+2+ COCO332-2-2. Check to see if

charges are balanced.

They are balanced!


Example: Zinc hydroxide


ZnZn2+2+ OHOH--2. Check to see if charges are balanced.


Not balanced!

( )( )22


Example: Aluminum phosphate


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

atoms, molecules, and ions. chemistry timeline #1 b.c. 400 b.c. demokritos and leucippos use the...

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