Atoms-Molecules-Ions Dr. Ron Rusay Fall 2007 © Copyright 2007 R.J. Rusay

Atoms-Molecules-Ions

Dr. Ron RusayDr. Ron Rusay

Fall 2007Fall 2007

© Copyright 2007 R.J. Rusay© Copyright 2007 R.J. Rusay

Aspects of Matter

•Elements, Compounds, and Mixtures (Part 1)•Atomic Theory Today•Elements: The Periodic Table•Ions & Compounds•Compounds: Introduction to Ionic Bonding•Compounds: Formulas & Names (Part 2)•Mixtures: Separation Techniques (Part 3)•Atomic & Molar Masses (Part 4)

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.http://www.yrbeyrbe.edu.on.ca/~.edu.on.ca/~mdhsmdhs/science/chemistry/ch2_2./science/chemistry/ch2_2.htmhtm

1927: Waves & Particles, Quantum Mechanics1927: Waves & Particles, Quantum Mechanicshttp://www.http://www.nmsinmsi.ac.uk/on-line/electron/section3/1927.html.ac.uk/on-line/electron/section3/1927.html

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

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© Copyright 1998- 2007 R.J. Rusay© Copyright 1998- 2007 R.J. Rusay

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






http://www.nmsi.ac.uk/on-line/electron/secton3/1927.html



http://www.nmsi.as.uk/on-line/electron/section3/1932a.html



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.http://www.nmsinmsi.ac.uk/on-line/electron/section2/.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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© Copyright 1998 - 2007 R.J. Rusay© Copyright 1998 - 2007 R.J. Rusay

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



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

Milliken Oil Drop Experiment

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

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).

http://www.eamesoffice.com/powers_of_ten/powers_of_ten.html



http://www.powersof10.com/

• 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

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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© Copyright 1998-2007 R.J. Rusay© Copyright 1998-2007 R.J. Rusay

Periodic Table1


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

QUESTIONThe element found in the 6A family (or group 16) and period four can be toxic and a micronutrient. What is the symbol for that element? You can use any help aid to answer this question except a breathing resource.

1. Sb2. As3. Se4. 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?

QUESTIONWhich of the following are incorrectly paired?1) Phosphorus, Ph2) Palladium, Pd3) Platinum, Pt4) Lead, Pb5) Potassium, K

QUESTIONOf the following which would not be considered a metalloid?

1. Ge2. Sb3. Se4. Spockonium, element #182 in the Star Trek Periodic Table.

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

Group 1 and Group 2 Metals

QuickTime™ and aCinepak decompressor

are needed to see this picture.

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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QUESTIONWhich among the following represent a set of isotopes? Atomic nuclei containing:

a. 20 protons and 20 neutrons. b. 21 protons and 19 neutrons. c. 22 neutrons and 18 protons. d. 20 protons and 22 neutrons. e. 21 protons and 20 neutrons.

1) a, b, c

2) c, d 3) a, e 4) a, d and b, e 5) No isotopes are indicated.

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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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

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

QUESTIONThe average mass of a carbon atom is 12.011. Assuming you were able to pick up only one carbon unit, the chances that you would randomly get one with a mass of 12.011 is 1) 0%. 2) 0.011%. 3) about 12%. 4) 12.011%. 5) greater than 50%.

Atomic SymbolsAtomic Symbols

K Element Symbol

39

19

Mass number

Atomic number

Also written as 39K



• 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



• 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

22

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…

1. positive and called an anion.2. positive and called a cation.3. negative and called an anion.4. negative and called a cation.

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

1. 36Cl2. 35Cl–

3. 37Cl–

4. 37Cl

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: Pg. 157Lab Manual: Pg. 157

Polyatomic Ionshttp://chemconnections.llnl.gov/general/Chem120/polyatomics.html

http://chemconnections.llnl.gov/general/Chem120/polyatomics.html

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

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--

QUESTIONAll of the following are true except: 1) Ions are formed by adding electrons to a

neutral atom. 2) Ions are formed by changing the number of

protons in an atom’s nucleus. 3) Ions are formed by removing electrons from

a neutral atom. 4) An ion has a positive or negative charge. 5) Metals tend to form positive ions.

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?

MgClMgCl2 2 CClCCl4 4 NaOHNaOH (NH(NH4 4 ))22COCO33

CC20 20 HH26 26 NN2 2 OO (Ibogaine, not ionic)(Ibogaine, not ionic)

QUESTIONHow many oxygen atoms are there in one formula unit of Ca3(PO4)2? 1) 2 2) 4 3) 6 4) 8 5) None of these

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Atoms-Molecules-Ions Dr. Ron Rusay Fall 2007 © Copyright 2007 R.J. Rusay