The Atom’s Family
NBSP Physical Science
Leadership Institute
Professor Lynn Cominsky
Joanne del Corral
Al Janulaw
Michelle Curtis
July 3, 2003
Standard Connections



Students know that all matter is made of
small particles called atoms, too small to
see with the naked eye (3)
Students know that all matter is made of
atoms…(5)
Students know that each element is made of
one kind of atom… (5)
7/3/2003
Prof. Lynn Cominsky
2
Some questions about the atom





What is an atom?
What are the parts of an atom?
How do we “see” the parts of the atom?
What is the structure of the atom?
Students know the structure of the atom,
and know it is composed of protons,
neutrons and electrons (8)
7/3/2003
Prof. Lynn Cominsky
3
Atoms – the historical view



Students know people once thought that earth,
wind, fire and water were the basic elements that
made up all matter (3)
The Greek Empedocle (around 492-432 BC.)
divided matter into four elements, that he also
called "roots": earth, air, fire and water
The word "atom" comes from the greek "atomos" and signifies "indivisible". This notion
was invented by Leucippe of Milet in 420 BC
7/3/2003
Prof. Lynn Cominsky
4
Atoms – the historical view

In ancient times, many elements were known,
including C, S, Cu, Ag, Au, Fe, Sn, Sb and Pb.
The names of most of these are from the Latin
words.

From 1000-1869, about 50
additional elements were
discovered, many by
alchemists, including As, Zn,
P, Pt, Ni, N, O, Cl and Al.
7/3/2003
Prof. Lynn Cominsky
5
History (continued)

Mendeleyev’s periodic table (1869)
classified and sorted elements based
on common chemical properties. His
table had 62 known elements, and left
space for 20 elements that were not
yet discovered. The elements were
arranged in order of atomic number.
7/3/2003
Prof. Lynn Cominsky
6
History (continued)


The electron was discovered in 1897 by
Thomson. He imagined the atom as a
“raisin pudding” with electrons stuck in a
cake of positive charge
In 1912, Rutherford discovered the
nucleus by doing scattering
experiments. He concluded the atom
was mostly empty space, with a large
dense body at the center, and
electrons which orbited the nucleus
like planets orbit the Sun
7/3/2003
Prof. Lynn Cominsky
7
History (continued)

Rutherford also realized that the nucleus must
contain both neutral and positively charged
particles. The neutron was then discovered in
1932 by Chadwick.
7/3/2003
Prof. Lynn Cominsky
8
First activity – Rutherford revisited



Given: a large wooden board, a mystery shape
and marbles
Try to identify the shape that is hiding under the
wooden board. You can only roll marbles against
the hidden object and observe the deflected paths
that the marbles take. Take at least five minutes to
"observe" a shape. Then do a second shape.
Place a piece of paper under the board for
sketching the paths of the marbles. Then analyze
this information to determine the object's actual
shape.
7/3/2003
Prof. Lynn Cominsky
9
Rutherford activity analysis




7/3/2003
Black vertical line shows
path of incoming marble
Red line shows path of
outgoing marble
Green dotted line bisects
the angle made by the
incoming and outgoing
lines
Reflecting surface is
perpendicular to bisecting
line
Prof. Lynn Cominsky
10
Questions about Rutherford activity




Draw a small picture of each shape you studied in
your lab notebook.
Can you tell the size of the object as well as its
shape?
How could you find out whether the shape has
features that are small compared to the size of
your marbles?
Without looking, how can you be sure of your
conclusions?
7/3/2003
Prof. Lynn Cominsky
11
What Rutherford really did


Rutherford shot alpha-particles (Helium nuclei) at
a thin gold foil. He found that most went right
through. However, some were deflected, and a
percentage of those bounced right back at him!
He said that “it was like firing a cannonball at
tissue paper, and having it ricochet off!”
Can you see how he concluded that the nucleus
was a hard small sphere, and that most of the
atom was empty space? (As opposed to a plum
pudding?)
7/3/2003
Prof. Lynn Cominsky
12
Vocabulary





Electron: negatively charged fundamental
particle
Proton: positively charged fundamental
particle
Neutron: uncharged fundamental particle
Nucleus: small, central unit in the atom that
contains neutrons and protons
Atom: smallest unit of an
element
7/3/2003
Prof. Lynn Cominsky
13
ELD Activities: Analogies, Imagery and
Student Involvement





Rutherford simplified -- Have a small group of
students (5-6) represent an atomic nucleus, by
standing in a circle facing outward.
Have the rest of the students stand around at random
spots, to represent the alpha particles.
Assign these students a straight path - either toward
the circle or missing it.
If they bump into the circle, they should turn around
and the children in the circle gently push them back
to where they came from.
Some will bounce back and some will keep going.
7/3/2003
Prof. Lynn Cominsky
14
Publisher’s Materials

Take some time to look through the stateadopted texts to find activities relating to
atoms that could be used in your
classroom.
7/3/2003
Prof. Lynn Cominsky
15
Break – some things to think about


We all know that “opposites attract” and
“like charges repel” –SO:
If electrons are negatively charged and
protons are positively charged, why don’t
the electrons fall into the nucleus?
?
7/3/2003
Prof. Lynn Cominsky
16
Standard connections



Science experiments show that there are
more than 100 different types of atoms, which
are presented in the periodic table of the
elements (3)
Students know that the elements are
organized in the periodic table by their
chemical properties (5)
Students know how to use the periodic table
to identify elements in simple compounds (8)
7/3/2003
Prof. Lynn Cominsky
17
Some questions:



What is an element?
Why are nuclei and atoms stable?
What is a molecule?
http://www.caffeinearchive.com/images/molecule.gif
7/3/2003
Prof. Lynn Cominsky
18
Key Concepts and Vocabulary: Atoms,
Elements and Molecules



Atom: smallest unit of an element
Element: any of more than 100 fundamental
substances that consist of atoms of only one kind
Molecule: a collection of atoms, bound together.


7/3/2003
Molecules can be made from only one element, such
as H2 or O2
Molecules can be made from different elements, such
as H2O or CO2
Prof. Lynn Cominsky
19
Parts of an Atom

Each element in the Periodic Table has a different number of
protons in its nucleus




p
The element also has the same number of electrons




Protons have positive charge
Change the number of protons  change elements
This is called nuclear physics
Electrons have negative charge
Change the number of electrons  ionize the element
This is called chemistry
e
Some elements also have neutrons


7/3/2003
Neutrons have no charge
They are in the nuclei of atoms
Prof. Lynn Cominsky
n
20
The Hydrogen Atom
• One electron orbiting a nucleus
• 1 proton = Z = atomic number
• 0 neutrons = N
p
• Total mass = A = Z+N =1
e
1H
7/3/2003
• Singly ionized Hydrogen is
missing one electron = 1H+
• Add a neutron and you have
Deuterium = 2H = D
Prof. Lynn Cominsky
21
The Helium Atom
• Two electrons orbiting a nucleus
e
p
n
n
p
e
4He
7/3/2003
• 2 protons = Z = atomic number
• 2 neutrons = N
• Total mass = A = Z+N =4
• Singly ionized Helium is missing
one electron = 4He+
• Doubly ionized Helium is missing
both electrons = a particle = 4He++
Prof. Lynn Cominsky
22
Isotopes and Elements
e

p
n
n
If Helium loses one of its
protons (and one of its
electrons), it becomes a
different element
3H (Tritium)

If Helium loses one of its
neutrons, it becomes an isotope
3He
7/3/2003
e
p
n p
e
Prof. Lynn Cominsky
23
History of the atom (Part 2)


Following Rutherford’s planetary model of the
atom, it was realized that the attraction between
the electrons and the protons should make the
atom unstable
Bohr proposed a model in which the electrons
would stably occupy fixed orbits, as long as these
orbits had special quantized locations
7/3/2003
Prof. Lynn Cominsky
24
History of the atom (continued)

In the Bohr model, the electron can
change orbits, accompanied by the
absorption or emission of a photon of a
specific color of light.
7/3/2003
Prof. Lynn Cominsky
25
History of the atom (continued)

Modern quantum theories lead to stable
locations of electrons, which are not exact
planetary orbits, but are characterized by
specific quantum numbers.

Each electron shell is
characterized by a
different principle
quantum number, usually
called n.
7/3/2003
Prof. Lynn Cominsky
26
History of the atom (continued)

In quantum theory, the
electron shells are not fixed
orbits, but clouds of
probability. You can’t
measure the exact location
of the electron.

Each electron orbital has a
different shape, and no
two electrons can be in the
same orbital (unless they
have opposite spins.)
7/3/2003
Prof. Lynn Cominsky
27
History of the atom (continued)

The quantum rules for
the electron orbitals in
an atom determine the
row structure in the
periodic table.

The geometry of the
electron orbitals
determines the structure
of an atom
7/3/2003
Prof. Lynn Cominsky
28
History of the atom (continued):
The spin of the electron is another
quantum property. In the planetary
model, it is similar to the spin of the
Earth on its axis. There are two
choices for the orientation of the
electron’s spin axis: up or down.

Some further questions:


What is periodic about the periodic table?
What types of chemical properties are used
to classify the elements?
7/3/2003
Prof. Lynn Cominsky
29
ELD Activity: Visual Imagery and
Identifying elements
Make a list of all the element names that
you know (e.g., Carbon, Oxygen, Silicon)
 What are some of the common household
items that contain these elements?
 Draw a picture of the items
Element
Item
Drawing

7/3/2003
Prof. Lynn Cominsky
30
Lunch puzzler

How do nuclei stay together when they are
filled with positive charges?
?
7/3/2003
Prof. Lynn Cominsky
31
Periodic Table of the Elements
Review: What
are the numbers
in each box?
7/3/2003
Prof. Lynn Cominsky
32
Navigating the Periodic Table


The rows are the “periods”
 Each period starts a new shell of electrons
 The periods are numbered starting with 1 at
the top
The columns are the “groups”
 Each group has similar chemical properties
 The groups are numbered starting with 1 at
the left
 Elements with similar properties have the
same number of electrons in the outermost
shell
7/3/2003
Prof. Lynn Cominsky
33
Electron shells and atomic structure


The first shell will hold up to two electrons.
The orbital is spherical, and called 1s. The
first row of the periodic table consists of 2
elements with 1s electrons.
The second (and third) rows each add eight
electrons. The shells that are filled are made
of a spherical orbital that holds 2 electrons,
called 2s or 3s, and 3 non-spherical orbitals
that hold a total 6 electrons, called 2p or 3p.
7/3/2003
Prof. Lynn Cominsky
34
Electron shells and atomic structure
p-orbitals

In the fourth row of the periodic table, the
4s orbital fills first, then a new orbital, 3d,
begins to be filled. It can hold 10 electrons.
7/3/2003
Prof. Lynn Cominsky
35
Electron shells and atomic structure
d-orbitals


What orbital is being filled in row 4 after 3d
is filled?
What is the pattern that repeats in row 5?
7/3/2003
Prof. Lynn Cominsky
36
Electron shells and atomic structure



In row 6, a new type of orbital, 4f, appears in
between elements 57 and 72. All the elements
with 4f electrons have very similar chemical
properties. They are known as the Lanthanides
(after element Z=57, Lanthanum) or rare earths.
A similar pattern repeats in row 7, with the 5f
orbitals filling between elements 89 and 104.
These elements also have similar chemical
properties, and are called the Actinide elements
(after element Z=89, Actinium).
There are 7 different f-orbitals: each can hold 2
electrons for a total of 14 in the 4f or 5f orbitals.
7/3/2003
Prof. Lynn Cominsky
37
Third activity: Shell structure




Carbon=C
Sodium=Na
Neon=Ne
Chlorine=Cl
e
p
p
p
e
e
Review:
what is this
element?
How many protons and electrons do these
elements have?
Draw the electron shell structure for each.
7/3/2003
Prof. Lynn Cominsky
38
Shell structure: thinking deeper





Where are the elements with very stable outer
shells in the periodic table? What do we call
them?
Where are the elements with one electron outside
a filled shell?
Where are the elements that need one electron to
fill their shells?
What happens when these two types of elements
are combined chemically?
So, what are some rules for making molecules?
7/3/2003
Prof. Lynn Cominsky
39
Key concepts: Periodic Table




The number of elements in each of the horizontal
rows (periods) in the periodic table, are due to the
quantum rules that govern the electron orbitals.
In vertical columns (groups) in the periodic table,
similar chemical properties are due to the number
of electrons in filled or unfilled shells.
Completely filled shells make an atom very stable
Elements with 1 or 2 electrons outside of filled
shells or with 1 or 2 missing electrons are very
chemically reactive. They always try to combine
with other elements that can fill their shells.
7/3/2003
Prof. Lynn Cominsky
40
Vocabulary




Atomic number: the number of protons in
the nucleus of an element
Atomic mass: the total mass in one atom of
an element
Ionization: removal of electrons from an
atom
Quantum: a very small discrete unit of light
or energy
7/3/2003
Prof. Lynn Cominsky
41
ELD Activities:Academic Language


What is meant by the phrase quantum leap?
Is this phrase consistent with the scientific
definition of the word quantum?
ELD Activities:Visual Imagery

Use modeling clay to represent atomic
structure. Use different colors for protons,
neutrons and electrons. Have the students
try different combinations for different
elements
7/3/2003
Prof. Lynn Cominsky
42
Publisher’s Materials


Take some time to look through the stateadopted texts to find activities relating to
the periodic table that could be used in
your classroom.
Examples: HC p. C46
7/3/2003
Prof. Lynn Cominsky
43
Thinking deeper: The forces in the atom



Electrons are bound to nucleus
by the Coulomb
(electromagnetic) force
Protons in nucleus are held
together by the strong nuclear
force
Neutrons can decay into protons
by weak nuclear force, emitting
an electron and an anti-neutrino.
The weak force is also
responsible for radioactivity.
7/3/2003
Prof. Lynn Cominsky
F = k q 1 q2
r2
n=p+e+n
44
Thinking deeper: The forces in the atom

There are four fundamental forces in physics.

Gravity and the electromagnetic
forces both have infinite range but
gravity is 1036 times weaker at a
given distance
The strong and weak forces are
both short range forces (<10-14 m)
The weak force is 10-8 times
weaker than the strong force
within the nucleus


7/3/2003
Prof. Lynn Cominsky
45
Standard connections


Students know metals have properties in
common, such as high electrical
conductivity (5)
The organization of the periodic table is
based on the properties of the elements and
reflects the structure of atoms. Students
know how to identify regions corresponding
to metals, nonmetals and inert gases (8)
7/3/2003
Prof. Lynn Cominsky
46
Fourth Activity: Electrical conduction





How can we tell which elements are good
electrical conductors?
Are all metals good conductors?
Are all good conductors metals?
How can we tell which materials are good
electrical insulators?
How do you think the electrons in
conductors differ from those in insulators?
7/3/2003
Prof. Lynn Cominsky
47
Equipment for Electrical Conduction
activity





Insulated wires
Batteries
Bulbs
Other things like rubber, wood, glass,
plastic, aluminum, paper clips, etc.
Masking tape
7/3/2003
Prof. Lynn Cominsky
48
More questions for Electrical
Conduction activity




Were you surprised by the some of the
items that were conductors?
Were you surprised by some of the items
that were insulators?
What did the conductors have in common?
What did the insulators have in common?
7/3/2003
Prof. Lynn Cominsky
49
Electrical Conductors: A deeper look



The best conductors are Copper (Cu), Silver
(Ag) and Gold (Au)
Cu has Z=29, Ag has Z=47 and Au has Z=79
How are these electrons arranged?
29 = 2+8+8+10+1
47 = 2+8+8+18+10+1

79 = 2+8+8+18 +
18+14+10 +1
So, why are these elements good conductors?
7/3/2003
Prof. Lynn Cominsky
50
Key concepts: Electrical Conductors




Conductors are usually (but not always) metals – they
have electrons that move easily, as they are outside
filled shells
Insulators are materials that block the flow of
electrons. They do not have easily removed electrons.
Metals occur where the d-orbitals are being filled in
the periodic table.
When you flip the switch, individual electrons do not
instantaneously move through the entire length of the
wire. Rather, they quickly bump into the metal nuclei,
as they slowly drift down the wire (at about 0.5
mm/sec)
7/3/2003
Prof. Lynn Cominsky
51
Vocabulary

Conductor: material that allows the flow of
electricity

Insulator: material that blocks the flow of
electricity
7/3/2003
Prof. Lynn Cominsky
52
ELD Activities: Academic Language




Writing and talking aloud help the students to
better process information:
The person who leads an orchestra or a band is
called a conductor. How is an orchestra conductor
similar to an electrical conductor?
Buildings stay warm because of insulation
material. How is insulation material similar to
electrical insulators?
Share your ideas and opinion with a partner and
write it in your journals in your own words.
7/3/2003
Prof. Lynn Cominsky
53
Reading connections



Read this article for students about the
discovery of the electron.
Read the longer article at home over the
weekend.
Reading strategy:



7/3/2003
Text to text
Text to self
Text to world
Prof. Lynn Cominsky
54
Takeaway – fireworks puzzler

What is the science behind the different
colors that you see when you watch the
July 4 fireworks?
7/3/2003
Prof. Lynn Cominsky
55
Lesson Study Activities



Identify a key concept from today’s lecture
for further development
Review the publisher’s materials about this
key concept
Think about the best way to present this
key concept in your classroom
7/3/2003
Prof. Lynn Cominsky
56
Resources

http://chemicool.com/

http://www.ill.fr/dif/3D-crystals/magnets.html
http://perso.club-internet.fr/molaire1/e_histoire.html
http://www.shodor.org/chemviz/ orbitals/sorbital.gif
http://members.aol.com/ChangChem/porbital.gif
http://members.aol.com/ChangChem/dorbital.gif





Physics by Inquiry – L. McDermott and the PEG
at U Washington

http://www.slac.stanford.edu/pubs/beamline/27/1/27-1-pais.pdf
http://www.cc.oulu.fi/~kempmp/colours.html

7/3/2003
Prof. Lynn Cominsky
57