Atoms-Molecules-Ions
Dr. Ron Rusay
Spring 2008
© Copyright 2008 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-

1913-19: Rutherford & Bohr’s atom;
The proton.
1
http://www.yrbe.edu.on.ca/~mdhs/science/chemistry/ch2_2.htm

1927: Waves & Particles, Quantum Mechanics
http://www.nmsi.ac.uk/on-line/electron/section3/1927.html

1932: James Chadwick “discovers” the neutron
http://www.nmsi.ac.uk/on-line/electron/section3/1932a.html
© Copyright 1998- 2008 R.J. Rusay
CHEMISTRY of the Atom
Ernest Rutherford (1871-1937)
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Modern History of the Atom
1
1897: J.J. Thomson “discovers” the electron:
http://www.nmsi.ac.uk/on-line/electron/section2/
Photo © The Nobel Foundation
http://pl.nobel.se/laureates/physics-1906-1-bio.html
© Copyright 1998 - 2008 R.J. Rusay
Milliken Oil Drop Experiment
QuickTime™ and a
Sorenson Video decompressor
are 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).
~ 0.1 nm
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
Nucleus =
1/10,000
of the atom
Can we “see” and
manipulate atoms
using a microscope?
Yes, using atomic force microscopy (AFM) and
a variety of instruments such as Scanning
Transmission Electron Microscopes.
TEAM 0.5:
LBL’s Latest (2008)
Transmission
Electron
Aberration-corrected
Microscope
Resolution:
• 1 nm = 10 Å
+/- 0.5 Å
• An atom vs. a nucleus
~10,000 x larger
Atomic/molecular structures atom-by-atom
Building of a quantum
“corral” with Fe atoms on Cu
Xe atoms on Ni(110)
STM images courtesy of Don Eigler, IBM, San Jose
Imaging: acetylene on Pd(111) at 28 K
Molecular Image
Tip cruising altitude ~700 pm
Δz = 20 pm
H
C
C
H
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
Surface atomic profile
Tip cruising altitude
~500 pm
Δz = 2 pm
TIP
pz
H
+
O
p orbital
Calculated image
(Philippe Sautet)
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
The STM image is a map of the pi-orbital
of distorted acetylene
M. Salmeron (LBL)
1 cm
(± 1 μm)
Excitation of frustrated rotational modes in
acetylene molecules on Pd(111) at T = 30 K
Tip
e-
QuickTime™ and a Y UV420 codec decompressor are needed to see this pict ure.
((( ) (
)))
M. Salmeron (LBL)
CHEMISTRY of the Atom
1
FUNDAMENTAL PARTICLES:
Mass
Charge
Nucleus:
 PROTON
1 amu
+1
Symbol
H+, H, p
• 1.67 x 10 -27 kg

NEUTRON
1 amu
0
n
• 1.67 x 10 -27 kg
_________________________________________
 ELECTRON very small -1
e•  2000 x smaller than a proton or neutron
The particle is said to “hold” or “bond” atoms together in
molecules.
© Copyright 1998-2008 R.J. Rusay
Periodic Table
1
• Mendeleev’s Table 1868-1871
Mural at St.Petersburg University, Russia
© Copyright 1998-2008 R.J. Rusay
QUESTION
The 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.
2.
3.
4.
Sb
As
Se
Te
ANSWER
Choice 3 pinpoints an element in both the 6A column and row
four. Remember to include the first row of Hydrogen and
Helium when counting rows.
Section 2.7: An Introduction to the Periodic Table
Chemical Symbols & Historical Names
1
What is the symbol for gold and what was its
original name?
QUESTION
Which of the following are incorrectly paired?
1) Phosphorus, Ph
2) Palladium, Pd
3) Platinum, Pt
4) Lead, Pb
5) Potassium, K
ANSWER
1)
Phosphorus, Pr
Ph
Section 2.7 An Introduction to the Periodic Table
(p. 55)
Phosphorus has a symbol of P.
QUESTION
Of the following which would not be considered a metalloid?
1. Ge
2. Sb
3. Se
4. Spockonium, element #182 in the Star Trek Periodic
Table.
ANSWER
Choice 3, Se, is the only element (without considering the
possibility of the fictional Spockonium) listed that is not on
the accepted Periodic Table’s “stairway” between metals and
nonmetals, therefore it is the only non-metalloid listed.
Section 2.7: An Introduction to the Periodic Table
Periodic Table

Elements are classified by:
properties & atomic number
metals, non-metals, metalloids

Groups or Families (vertical)
1A = alkali metals
2A = alkaline earth metals
6A (16) = chalcogens
7A (17) = halogens
8A (18) = noble gases

Periods (horizontal) numbers 1-7
Group 1 and Group 2 Metals
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Using the Periodic Table
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Atoms, Molecules & Ions
1
 Atoms (neutral electrostatic charge: # protons
= # electrons )
• # Protons = Atomic Number
• Atomic Mass = # Protons + # of Neutrons
• Isotope: same atomic number but different atomic
mass (different # of neutrons)
© Copyright 1998-2008 R.J. Rusay
QUESTION
Which among the following represent a set of
isotopes? Atomic nuclei containing:
a.
b.
c.
d.
e.
20 protons and 20 neutrons.
21 protons and 19 neutrons.
22 neutrons and 18 protons.
20 protons and 22 neutrons.
21 protons and 20 neutrons.
1)
2)
3)
4)
5)
a, b, c
c, d
a, e
a, d and b, e
No isotopes are indicated.
ANSWER
4)
a, d and b, e
Section 2.5 The Modern View of Atomic
Structure: An Introduction (p. 49)
Isotopes have the same number of protons and
different numbers of neutrons, so they can be
organized by atomic number.
Atoms, Molecules & Ions
1
• Isotopes vary in their relative natural
abundance.
• Periodic Table’s atomic mass is a
weighted average of all isotopic masses
• The mass of sodium, Na, element #11 is
listed as 22.99 amu. Which isotope is
naturally present in the larger amount:
the isotope with 12 neutrons or with 13
neutrons? (There is a small percentage
of the isotope with 11 neutrons.)
© Copyright 1998-2008 R.J. Rusay
Atoms, Molecules & Ions
1

Atomic Mass of Carbon:
Exact Mass
% Occurence
12.00000
98.98
13.00335
1.011
14.00
negligible
What is the “weighted” atomic mass?
12.00000 x 98.98/100 + 13.00335 x 1.011 =
© Copyright 1998-2008 R.J. Rusay
11.8776 + 0.13146 = 12.0090

12.01
Atoms, Molecules and Ions
1
•
•
•
•
•
Atomic Number = 6 (atom’s identity)
Carbon
Atomic Mass = 13 (isotope 13)
6 protons; # neutrons = 13 - 6
neutral atom has 6 electrons
© Copyright 1998-2008 R.J. Rusay
QUESTION
The 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%.
ANSWER
1)
0%.
Section 3.1 Atomic Mass (p. 77)
The 12.011 is an average of the isotopic
masses. None of the isotopes has an exact mass of
12.011.
Atomic Symbols
Mass number 
39
K
19
 Element Symbol
Atomic number 
Also written as 
39
K
Atoms, Molecules and Ions
1
•
•
•
•
•
Atomic Number = 12 (atom’s identity)
Atomic Mass = 24
12 protons; # neutrons = 24 - 12
neutral atom has 12 electrons
Ion contains 10 electrons: symbol?
24
12
+2
Mg
• 12 p+ + 10e- = +2
© Copyright 1998-2008 R.J. Rusay
Atoms, Molecules and Ions
1
•
•
•
•
•
Atomic Number = 17 (atom’s identity)
Atomic Mass = ?
# protons = ? ; # neutrons = ?
neutral atom has ? electrons
Ion contains 18 electrons: symbol?
35
17
-1
Cl
• 17 p+ + 18e- = -1
© Copyright 1998-2008 R.J. Rusay
Ions
 Cation:
 Anion:
 Ionic
A positive ion
 Mg2+, NH4+
A negative ion
 Cl, SO42
Bonding: Force of attraction
between oppositely charged ions.
QUESTION
Calcium 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.
2.
3.
4.
positive and called an anion.
positive and called a cation.
negative and called an anion.
negative and called a cation.
ANSWER
Choice 2 provides the correct relationship and name for an
atom of calcium (20 protons = 20+) that has lost two electrons
(now with 18–). The ion would have a +2 charge. Positive
ions are called cations.
Section 2.6: Molecules and Ions
QUESTION
Of the following, which would NOT qualify as an isotope of
35Cl?
1.
2.
3.
4.
36Cl
35Cl–
37Cl–
37Cl
ANSWER
Choice 2 is NOT an isotope of 35Cl. All three choices represent a
form of chlorine but choice 2 has the same number of neutrons
as the atom in the question, therefore it does not fit the criteria
for isotopes (i.e. variable neutron number with constant proton
number). Isotopes can be ions as well as neutral atoms. 37Cl–
and 37Cl are also not isotopes.
Section 2.5: The Modern View of Atomic Structure: An
Introduction
Worksheet: Atoms I
Lab Manual: Pg. 157
Nuclear
Symbol
12
6
C
14
7
N
Number of
Proto ns
6
Number of
Neutrons
6
Number of
Electro ns
6
7
7
8
7
18
17O2–
56Fe
19F–
Atomic
Mass
Number (Z) Number (A)
6
12
20
8
26
9
40
Polyatomic Ions
http://chemconnections.llnl.gov/general/Chem120/polyatomics.html
Molecules
 Neutrally
Charged
 Eg. Salt: NaCl -> 1 Na+ and 1 Cl  What is the proportion of ions for a
compound formed from Mg ion and
chlorine?
 Mg2+ and Cl
 1 Mg2+ combines with 2 Cl
Ionic vs. Covalent
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Ionic vs. Covalent
Metals generally combine with non- metals to
form ionic compounds. Electrons are “lost” by
the metal and “gained” by the non-metal
following the octet rule.
 Non-metals generally combine with nonmetals to form covalent compounds where
electrons are “shared”. Each pair of electrons
ia a covalent bond. Eg. H2O
 Polyatomic ions have both covalent and ionic
properties. Eg. hydroxide, OH
QUESTION
All 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.
ANSWER
2)
Ions are formed by changing the number of
protons in an atom’s nucleus.
Section 2.6 Molecules and Ions (p. 52)
The removal of a proton from the nucleus
requires extraordinary amounts of energy. It will
only happen during a nuclear reaction.
Chemical Formulas
 Molecular
Formula:
Elements’ Symbols = atoms
Subscripts = relative numbers of atoms
 How many atoms of each element are in
the following componds?
MgCl2
CCl4
NaOH
(NH4 )2CO3
C20 H26 N2 O (Ibogaine, not ionic)
QUESTION
How 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
ANSWER
4)
8
Section 2.8 Naming Simple Compounds (p. 57)
57
Remember to multiply the number of oxygen
atoms in the parentheses by the subscript
outside of the parentheses.