Atoms-Molecules-Ions

Dr. Ron RusayDr. Ron Rusay

Atoms, Compounds, and the Periodic Table

2.1 The Early History of Chemistry2.2 Fundamental Chemical Laws2.3 Dalton's Atomic Theory2.4 Early Experiments to Characterize the Atom2.5 The Modern View of Atomic Structure: An Introduction2.6 Molecules and Ions2.7 An Introduction to the Periodic Table2.8 Naming Simple Compounds

Modern History of the Atom 1909: Millikan determines charge and mass of e-1909: Millikan determines charge and mass of e-

1913-19: Rutherford & Bohr’s atom;1913-19: Rutherford & Bohr’s atom;

The proton. The proton. http://www.yrbe.edu.on.ca/~mdhs/science/chemistry/ch2_2.htmhttp://www.yrbe.edu.on.ca/~mdhs/science/chemistry/ch2_2.htm

1926: Waves & Particles, Quantum Mechanics1926: Waves & Particles, Quantum Mechanicshttp://chemed.chem.purdue.edu/genchem/history/schrodinger.htmlhttp://chemed.chem.purdue.edu/genchem/history/schrodinger.html

1932: James Chadwick “discovers” the neutron1932: James Chadwick “discovers” the neutronhttp://www.nmsi.ac.uk/on-line/electron/section3/1932a.htmlhttp://www.nmsi.ac.uk/on-line/electron/section3/1932a.html

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CHEMISTRY of the AtomErnest Rutherford (1871-1937)

Modern History of the Atom1897: J.J. Thomson “discovers” the electron:1897: J.J. Thomson “discovers” the electron:

http://www.nmsi.ac.uk/on-line/electron/section2/http://www.nmsi.ac.uk/on-line/electron/section2/

Photo © The Nobel FoundationPhoto © The Nobel Foundation

http://pl.nobel.se/laureates/physics-1906-1-bio.htmlhttp://pl.nobel.se/laureates/physics-1906-1-bio.html

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Milliken Oil Drop Experiment

How does an atom relate to nanotechnology?

Consider Powers of 10 (10 x)http://www.eamesoffice.com/powers_of_ten/powers_of_ten.html

http://www.powersof10.com/

Earth = 12,760,000 meters wide (12.76 x 10 6), 12.76 million meters (megameters)

Plant Cell = 0.00001276 meters wide (12.76 x 10 -6) (12.76 millionths of a meter) (12,760 nanometers!)

Nano scale is regarded as < 1,000 nanometers ~1/50 the diameter of a human hair (anything less than a micron (10-6 m). Chemists typically think in views and images of < 1 nanometer (eg. bond lengths and atomic sizes).

• 1 nm = 10 Å• An atom vs. a nucleus ~10,000 x larger

~ 0.1 nm

Nucleus =1/10,000of the atom

Anders Jöns Ångström(1814-1874)

1 Å = 10 picometers = 0.1 nanometers = 10-4 microns = 10-8 centimeters

• 1 nm = 10 Å• An atom vs. a nucleus ~10,000 x larger

Can we “see” and Can we “see” and manipulate atoms manipulate atoms using a microscope?using a microscope?

Yes, using atomic force microscopy (AFM) and Yes, using atomic force microscopy (AFM) and a variety of instruments such as Scanning a variety of instruments such as Scanning Transmission Electron Microscopes.Transmission Electron Microscopes.

TEAM 0.5:TEAM 0.5:LBL’s LBL’s TTransmission ransmission EElectron lectron AAberration-corrected berration-corrected MMicroscopeicroscopeResolution:Resolution: +/- 0.5 +/- 0.5 Å

http://science.kqed.org/quest/video/the-worlds-most-powerful-microscope/

Xe atoms on Ni(110)

Atomic/molecular structures atom-by-atom

STM images courtesy of Don Eigler, IBM, San Jose

Building of a quantum “corral” with Fe atoms on Cu

C

C

H

H

Calculated image (Philippe Sautet)

orbital

pz

TIP

H

O+

Imaging: acetylene on Pd(111) at 28 K

Molecular Image Tip cruising altitude ~700 pmΔz = 20 pm

Surface atomic profile

Tip cruising altitude ~500 pm

Δz = 2 pm

1 cm(± 1 μm)

The STM image is a map of the pi-orbital of distorted acetylene

Why don’t we see the Pd atoms?Because the tip needs to be very close to image the Pd atoms and would knock the molecule away

If the tip was made as big as an airplane, it would be flying at 1 cm from the surface and waving up an down by 1 micrometer

M. Salmeron (LBL)

Excitation of frustrated rotational modes in acetylene molecules on Pd(111) at T = 30 K

Tip

e-

((( ) ( )))

M. Salmeron (LBL)

CHEMISTRY of the Atom

FUNDAMENTAL PARTICLES:FUNDAMENTAL PARTICLES: MassMass ChargeCharge SymbolSymbol

Nucleus:Nucleus: PROTON PROTON 1 amu 1 amu +1 +1 H+, H, p H+, H, p

• 1.67 x 10 1.67 x 10 -27-27 kg kg

NEUTRON NEUTRON 1 amu 1 amu 0 0 n n• 1.67 x 10 1.67 x 10 -27-27 kg kg

__________________________________________________________________________________ ELECTRON very small -1ELECTRON very small -1 e e - -

• 2000 x smaller than a proton or neutron2000 x smaller than a proton or neutron

The particle is said to “hold” or “bond” atoms together in molecules.

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Periodic Table1

• Mendeleev’s Table 1868-1871Mendeleev’s Table 1868-1871Mural at St.Petersburg University, RussiaMural at St.Petersburg University, Russia

Periodic TableLos Alamos National Lab

QUESTIONThe element found in the 6A family (or group 16) and period four can be toxic, a micronutrient, and found in compounds in dandruff shampoos. What is the symbol for that element?

A. SbB. AsC. SeD. Te

AnswerThe element found in the 6A family (or group 16) and period four can be toxic, a micronutrient, and found in compounds in dandruff shampoos. What is the symbol for that element?

A. SbB. AsC. SeD. Te

Chemical Symbols & Historical Names1

What is the symbol for gold and what was its What is the symbol for gold and what was its original name?original name?

http://chemconnections.org/general/movies/leher-elements.swf

QUESTION

Answer

QUESTIONOf the following which would not be considered a metalloid?

A. GeB. SbC. TeD. SeE. As

AnswerOf the following which would not be considered a metalloid?

A. GeB. SbC. TeD. SeE. As

Periodic TablePeriodic TablePeriodic TablePeriodic Table Elements are classified by:Elements are classified by:

properties & atomic numberproperties & atomic number

metals, non-metals, metalloidsmetals, non-metals, metalloids

Groups Groups or or Families Families (vertical)(vertical) 1A = alkali metals1A = alkali metals

2A = alkaline earth metals2A = alkaline earth metals

6A (16) = chalcogens6A (16) = chalcogens

7A (17) = halogens7A (17) = halogens

8A (18) = noble gases8A (18) = noble gases

Periods Periods (horizontal) (horizontal) numbers 1-7numbers 1-7

Select the correct statement relative to the modern periodic Select the correct statement relative to the modern periodic table.table.

A) Tin is a transition element.A) Tin is a transition element.

B) Lead is a nonmetal.B) Lead is a nonmetal.

C) Antimony is a metalloid.C) Antimony is a metalloid.

D) Elements are arranged in order of increasing atomicD) Elements are arranged in order of increasing atomic mass.mass.E) Sulfur is a halogen.E) Sulfur is a halogen.

QUESTION

Select the correct statement relative to the modern periodic Select the correct statement relative to the modern periodic table.table.

A) Tin is a transition element.A) Tin is a transition element.

B) Lead is a nonmetal.B) Lead is a nonmetal.

C) Antimony is a metalloid.C) Antimony is a metalloid.

D) Elements are arranged in order of increasing atomicD) Elements are arranged in order of increasing atomic mass.mass.E) Sulfur is a halogen.E) Sulfur is a halogen.

Answer

Group 1 and Group 2 Metals

Using the Periodic Table

Atoms, Molecules & Ions

Atoms Atoms (neutral electrostatic charge: (neutral electrostatic charge: # protons# protons = = # electrons# electrons )) • # Protons # Protons = = Atomic NumberAtomic Number• Atomic MassAtomic Mass = = # Protons# Protons + + # of Neutrons# of Neutrons• Isotope: same atomic number but different atomic Isotope: same atomic number but different atomic

mass (different # of neutrons)mass (different # of neutrons)

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QUESTION

Answer

Atoms, Molecules & Ions• Isotopes vary in their relative natural Isotopes vary in their relative natural

abundance.abundance.• Periodic Table’s atomic mass is a Periodic Table’s atomic mass is a

weighted average of all isotopic massesweighted average of all isotopic masses• The mass of sodium, Na, element #11 is The mass of sodium, Na, element #11 is

listed as 22.99 amu. Which isotope is listed as 22.99 amu. Which isotope is naturally present in the larger amount: naturally present in the larger amount: the isotope with 12 neutrons or with 13 the isotope with 12 neutrons or with 13 neutrons? (There is a small percentage neutrons? (There is a small percentage of the isotope with 11 neutrons.)of the isotope with 11 neutrons.)

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Two stable isotopes of an element have isotopic Two stable isotopes of an element have isotopic masses of 10.0129 amu and 11.0093 amu. The atomic masses of 10.0129 amu and 11.0093 amu. The atomic mass is 10.81. Which isotope is more abundant? mass is 10.81. Which isotope is more abundant?

A) There is insufficient information to answer A) There is insufficient information to answer the question. the question.

B) There are equal amounts of each isotope.B) There are equal amounts of each isotope.

C) The isotope with a mass of 10.0129 amu C) The isotope with a mass of 10.0129 amu is more abundant. is more abundant.

D) The isotope with a mass of 11.0093 amu D) The isotope with a mass of 11.0093 amu is more abundant. is more abundant.

QUESTION

Two stable isotopes of an element have isotopic Two stable isotopes of an element have isotopic masses of 10.0129 amu and 11.0093 amu. The atomic masses of 10.0129 amu and 11.0093 amu. The atomic mass is 10.81. Which isotope is more abundant? mass is 10.81. Which isotope is more abundant?

A) There is insufficient information to answer A) There is insufficient information to answer the question. the question.

B) There are equal amounts of each isotope.B) There are equal amounts of each isotope.

C) The isotope with a mass of 10.0129 amu C) The isotope with a mass of 10.0129 amu is more abundant. is more abundant.

D) The isotope with a mass of 11.0093 amu D) The isotope with a mass of 11.0093 amu is more abundant. is more abundant.

Answer

Atoms, Molecules & Ions

Atomic Mass of Carbon:Atomic Mass of Carbon:

What is the “weighted” atomic mass?What is the “weighted” atomic mass?

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Exact Mass % Occurence

12.00000 98.98

13.00335 1.011

14.00 negligible

12.00000 x 98.98/100 + 13.00335 x 1.011 =12.00000 x 98.98/100 + 13.00335 x 1.011 =11.8776 + 0.13146 = 12.009011.8776 + 0.13146 = 12.0090

12.0112.01

The two major isotopes of bromine are The two major isotopes of bromine are 7979Br and Br and 8181Br. Br. Assume that the masses of the Assume that the masses of the 7979Br and Br and 8181Br isotopes Br isotopes are 79.00 and 81.00 amu, respectively. The weighted are 79.00 and 81.00 amu, respectively. The weighted average atomic mass of bromine is 79.90 amu. average atomic mass of bromine is 79.90 amu.

What are the relative % abundances of each isotope? What are the relative % abundances of each isotope?

% Abundance of % Abundance of 7979BrBr % Abundance of % Abundance of 8181BrBr• 79.0%79.0% 21.0%21.0%

• 19.0%19.0% 81.0%81.0%

• 35.1%35.1% 64.9%64.9%

• 55.0%55.0% 45.0%45.0%

QUESTION

The two major isotopes of bromine are The two major isotopes of bromine are 7979Br and Br and 8181Br. Br. Assume that the masses of the Assume that the masses of the 7979Br and Br and 8181Br isotopes Br isotopes are 79.00 and 81.00 amu, respectively. The weighted are 79.00 and 81.00 amu, respectively. The weighted average atomic mass of bromine is 79.90 amu. average atomic mass of bromine is 79.90 amu.

What are the relative % abundances of each isotope? What are the relative % abundances of each isotope?

% Abundance of % Abundance of 7979BrBr % Abundance of % Abundance of 8181BrBr• 79.0%79.0% 21.0%21.0%

• 19.0%19.0% 81.0%81.0%

• 35.1%35.1% 64.9%64.9%

• 55.0%55.0% 45.0%45.0%

Answer

Atoms, Molecules and Ions1

• Atomic Number = 6 (atom’s identity)Atomic Number = 6 (atom’s identity)• CarbonCarbon• Atomic Mass = 13 (isotope 13)Atomic Mass = 13 (isotope 13)• 6 protons; # neutrons = 13 - 66 protons; # neutrons = 13 - 6• neutral atom has 6 electronsneutral atom has 6 electrons

QUESTION

AnswerNone of the isotopes has an exact mass of 12.011.

Atomic SymbolsAtomic Symbols

K Element Symbol

39

19

Mass number

Atomic number

Also written as 39K

Atoms, Molecules and Ions1

• Atomic Number = 12 (atom’s identity)Atomic Number = 12 (atom’s identity)• Atomic Mass = 24Atomic Mass = 24• 12 protons; # neutrons = 24 - 1212 protons; # neutrons = 24 - 12• neutral atom has 12 electronsneutral atom has 12 electrons• Ion contains 10 electrons: symbol?Ion contains 10 electrons: symbol?

• 12 p12 p++ + 10e + 10e-- = +2 = +2

Mg12

24 +2

Atoms, Molecules and Ions1

• Atomic Number = 17 (atom’s identity)Atomic Number = 17 (atom’s identity)• Atomic Mass = ?Atomic Mass = ?• # protons = ? ; # neutrons = ?# protons = ? ; # neutrons = ?• neutral atom has ? electronsneutral atom has ? electrons• Ion contains 18 electrons: symbol?Ion contains 18 electrons: symbol?

• 17 p17 p++ + 18e + 18e-- = -1 = -1

Cl17

35 -1

IonsIons

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.

QUESTIONCalcium plays several critical roles in the functioning of human cells. However, this form of calcium is the ion made with 20 protons and 18 electrons. Therefore the ion would be…

A. positive and called an anion.B. positive and called a cation.C. negative and called an anion.D. negative and called a cation.

AnswerCalcium plays several critical roles in the functioning of human cells. However, this form of calcium is the ion made with 20 protons and 18 electrons. Therefore the ion would be…

A. positive and called an anion.B. positive and called a cation.C. negative and called an anion.D. negative and called a cation.

An atom of calcium (20 protons = 20+) which has lost two electrons (now with 18–). The ion would have a +2 charge. Positive ions are called cations.

QUESTIONOf the following, which would NOT qualify as an isotope of 35Cl?

• 36Cl• 35Cl–

• 37Cl–

• 37Cl

AnswerOf the following, which would NOT qualify as an isotope of 35Cl?

• 36Cl• 35Cl–

• 37Cl–

• 37Cl

B. has the same number of neutrons as the atom in the question, therefore it does not fit the criteria for isotopes (i.e. different number of neutrons with the same proton number). Isotopes can be ions as well as neutral atoms. 37Cl– and 37Cl are also not a pair of isotopes.

NuclearSymbol

Number ofProtons

Number ofNeutrons

Number ofElectrons

AtomicNumber (Z)

MassNumber (A)

12  6 C

6 6 6 6 12

14  7 N

7

7 8 7

18 20 40

17O2– 8

56Fe 26

19F– 9

Worksheet: Atoms IWorksheet: Atoms I (Lab Manual)(Lab Manual)

Which of these species has the highest number of Which of these species has the highest number of electrons?electrons?

A) A) 2020CaCaB) B) 1919KK++ C) C) 1616SS22−− D) D) 1515PP33−−

QUESTION

Which of these species has the highest number of Which of these species has the highest number of electrons?electrons?

A) A) 2020CaCaB) B) 1919KK++ C) C) 1616SS22−− D) D) 1515PP33−−

Answer

The ion The ion 4545ScSc3+3+ has has

A) 24 electrons, 21 protons and 24 neutronsA) 24 electrons, 21 protons and 24 neutrons

B) 18 electrons, 21 protons and 24 neutronsB) 18 electrons, 21 protons and 24 neutrons

C) 24 electrons, 24 protons and 21 neutronsC) 24 electrons, 24 protons and 21 neutrons

D) 18 electrons, 24 protons and 21 neutronsD) 18 electrons, 24 protons and 21 neutrons

QUESTION

The ion The ion 4545ScSc3+3+ has has

A) 24 electrons, 21 protons and 24 neutronsA) 24 electrons, 21 protons and 24 neutrons

B) 18 electrons, 21 protons and 24 neutronsB) 18 electrons, 21 protons and 24 neutrons

C) 24 electrons, 24 protons and 21 neutronsC) 24 electrons, 24 protons and 21 neutrons

D) 18 electrons, 24 protons and 21 neutronsD) 18 electrons, 24 protons and 21 neutrons

Answer

Molecules

Neutrally ChargedNeutrally Charged Eg. Salt: NaCl -> 1 NaEg. Salt: NaCl -> 1 Na++ and 1 Cl and 1 Cl -- What is the proportion of ions for a What is the proportion of ions for a

compound formed from Mg ion and compound formed from Mg ion and chlorine?chlorine?

MgMg2+2+ andand Cl Cl

11 Mg Mg2+2+ combines with combines with 22 Cl Cl

MgClMgCl2 2

Predict the formula for the binary ionic compound formed by aluminum and oxygen.

A) Al2O3 B) Al3O2 C) Al2O D) AlO2

QUESTION

Predict the formula for the binary ionic compound formed by aluminum and oxygen.

A) Al2O3 B) Al3O2 C) Al2O D) AlO2

ANSWER

Polyatomic Ionshttp://chemconnections.org/general/chem120/polyatomics.html

Which formula containing polyatomic ions is correct?

A) MgNO3 B) NH4CO3 C) Na(PO4)3 D) Al2(SO4)3

QUESTION

Which formula containing polyatomic ions is correct?

A) MgNO3 B) NH4CO3 C) Na(PO4)3 D) Al2(SO4)3

ANSWER

Ionic vs. Covalent

Ionic vs. Covalent

Metals generally combine with non- metals to form Metals generally combine with non- metals to form ionic compounds. Electrons are “lost” by the metal ionic compounds. Electrons are “lost” by the metal and “gained” by the non-metal following the octet and “gained” by the non-metal following the octet rule.rule.

Non-metals generally combine with non-metals to Non-metals generally combine with non-metals to form covalent compounds where electrons are form covalent compounds where electrons are “shared”. Each pair of electrons ia a covalent “shared”. Each pair of electrons ia a covalent bond. Eg. Hbond. Eg. H22OO

Polyatomic ions have both covalent and ionic Polyatomic ions have both covalent and ionic properties. Eg. hydroxide, OHproperties. Eg. hydroxide, OH--

QUESTION

Answer

Chemical FormulasChemical Formulas

Molecular Formula:Molecular Formula:

Elements’ SymbolsElements’ Symbols = atoms = atoms

SubscriptsSubscripts = relative numbers of atoms = relative numbers of atoms How many atoms of each element are in How many atoms of each element are in

the following componds?the following componds?

MgClMgCl22 CClCCl4 4 NaOHNaOH (NH(NH44 ))22COCO33

CC2020 HH2626 NN22 OO (Ibogaine, not ionic)(Ibogaine, not ionic)

QUESTION

Answer