Defining the Atom
2. Structure of the Nuclear Atom
3. Distinguishing Between Atoms
1.
Date:
Honey Do List:
• Answer Bell-Ringer & write down new objectives
• HMWK: Read Ch.4 Section 1. Complete questions #1-5
on page 104 of text.
Bell-Ringer
 What components make up an atom?
 How are atoms of one element different from
atoms of another element?
1. Defining the Atom
What is an atom?
Atom – the smallest particle of an element that retains
its identity in a chemical reaction.
 Matter is composed of atoms
The Scale of an Atom
How can we measure atoms?
1. Defining the Atom
Early Models of the Atom
Democritus’s Atomic Theory
• 1st to suggest the existence of
atoms
• Believed atoms to be
indivisible and indestructible.
Democritus (460 B.C. – 370 B.C.)
Problems with theory…
• Lacked experimental support; not based on the
scientific method.
• Did not explain chemical behavior of atoms
1. Defining the Atom
Early Models of the Atom
John Dalton
• Used experimental methods to
transform Democritus’s ideas on the
atom into a scientific theory.
Dalton’s Atomic Theory
 Comprised of 4 KEY concepts
illustrated on the following slides.
1. Defining the Atom
Dalton’s Atomic Theory
1.
All elements are composed of tiny indivisible
particles called atoms.
1. Defining the Atom
Dalton’s Atomic Theory
2. Atoms of the same element are identical. The atoms
of any one element are different from those of any
other element.
1. Defining the Atom
Dalton’s Atomic Theory
3. Atoms of different elements can physically mix
together or can chemically combine in simple wholenumber ratios to form compounds.
1. Defining the Atom
Dalton’s Atomic Theory
4. Chemical reactions occur when atoms are separated,
joined, or rearranged. Atoms of one element are
never changed into atoms of another element in a
chemical reaction.
1. Defining the Atom
Sizing up the Atom
 A pure copper (Cu) penny
 Copper powder
 1 copper particle = atom
 Indivisible
 Copper penny = 2.4 x 1022 atoms
How small is an atom?
TED tv worksheet
1.
The ancient Greek philosopher credited with
suggesting all matter is made of indivisible atoms is
A.
B.
C.
D.
Plato.
Aristotle.
Democritus.
Socrates.
2. Dalton's atomic theory improved earlier atomic
theory by
A.
B.
C.
D.
teaching that all matter is composed of tiny
particles called atoms.
theorizing that all atoms of the same element
are identical.
using experimental methods to establish a
scientific theory.
not relating atoms to chemical change.
3. Individual atoms are observable with
A.
B.
C.
D.
the naked eye.
a magnifying glass.
a light microscope.
a scanning tunneling microscope.
November 3, 2014
The assignment for the next 2 days:
 History of the Atom Timeline Project
 Due Thursday, November 6, 2014
 Period 1 : 2 groups of 4
 Period 3: 4 groups of 4
 Period 4: whole class works as 1 group
 Period 7: 2 groups of 4 and 1 group of 3
Today’s date: Nov. 10, 2014
Bell Ringer
 Study the picture:
 How could you determine what your hand looks like
under the skin without dissecting it?
2. Structure of the Nuclear Atom
Connecting to Your World
 Today, cathode-ray tubes are found in TVs, computer
monitors, and many other devices with electronic
displays.
2. Structure of the Nuclear Atom
Subatomic Particles
 Subatomic particles – smaller, fundamental particles
that make up the atom.
Three kinds of subatomic particles are:
1.
ELECTRONS
2. PROTONS
3. NEUTRONS
Eddie the Electron is a busy lil’ guy that
gets excited and likes to bond with the
ladies. Too many negative experiences with
the brunettes has him favoring the blondes.
When ever down in the dumps, turn to Patty
the Proton; she always has a positive
attitude!
Stay in for dinner or go out? Nonconfrontational Neil the Neutron insists on
remaining neutral for all things with wife
Patty. “Happy wife, happy life”
Think – Write – Pair Share
 Cathode Ray Tube
 You are about to view a gas tube that is hooked up to a
power source. Silently observe what I am doing. I
want you to infer about what is occurring in this
interactive. Take 2 minutes to think about and write
down what you believe is happening.
2. Structure of the Nuclear Atom
Electrons
Eddie
Electrons – negatively charged subatomic particles
 Discovered in 1897 by English physicist J.J.
Thomson.
 Thomson performed experiments that
involved passing electric current through
gases at low pressure.
 The result was a glowing beam, or cathode
ray, that traveled from the cathode to the
anode.
 “Plum-pudding model” of the atom – electrons were
randomly distributed in a lump of positive charge, similar to
raisins stuck in dough.
2. Structure of the Nuclear Atom
Cathode Ray Tube
Electrons travel “-” to “+”
2. Structure of the Nuclear Atom
 A cathode ray is deflected by a magnet
Inferring: If a cathode ray is attracted to a positively
charged plate, what can you infer about the charge of the
particles that make up the cathode ray?
2. Structure of the Nuclear Atom
 A cathode ray is deflected by electrically charged plates.
 Thomson concluded that a cathode ray is a stream of
electrons. Electrons are parts of the atoms of all elements.
2. Structure of the Nuclear Atom
How Negative is Eddie?
 Thomson’s attempts:
 Measured the ratio of charge to the mass of an electron
 Found ratio to be constant
 U.S. Physicist Robert A. Millikan (1868 – 1953)
 How much charge is carried by an electron?
 Calculated the mass of the electron: 1/1840 the mass of a
hydrogen atom.
 Electron carries 1 unit of negative charge.
2. Structure of the Nuclear Atom
Protons
Protons – positively charged subatomic particles.
 Discovered in 1886 by Eugen Goldstein.
 Observed a cathode-ray tube and
found rays travelling in the opposite
direction to the cathode rays .
 Concluded that these rays were
positively charged
 Relative mass of proton = 1
 Supports that atoms are electrically
neutral
Patty
2. Structure of the Nuclear Atom
Neutrons
Neil
Neutrons – subatomic particles with no charge but with
a mass nearly equal to that of a proton.
• Discovered by English physicist James
Chadwick in 1932
2. Structure of the Nuclear Atom
Rutherford’s GoldFoil Experiment
 1911, Ernest Rutherford Gold-Foil Experiment
 Used a narrow beam of alpha () particles
directed at a thin sheet of gold foil.
 Prevailing theory:  particles would pass
easily through the gold foil with slight deflection due to
the positive charge spread throughout good atoms.
 Result: majority of  particles passed straight through,
others bounced off the gold foil at large angles, and some
even bounced directly back to the source.
2. Structure of the Nuclear Atom
Rutherford’s Gold-Foil Experiment
2. Structure of the Nuclear Atom
Rutherford’s Gold-Foil Experiment
 Alpha particles scatter from the gold foil.
2. Structure of the Nuclear Atom
THE NEW THEORY:
AKA – Nuclear Atom
All the positive charge and almost all the mass is
concentrated in a small region called the nucleus
1.

Explained the great deflection of some of the alpha
particles.
Nucleus – the tiny central core of an atom, composed of
protons and neutrons.
2. Structure of the Nuclear Atom
2. The atom is mostly empty space
 Explained the lack of deflection of most
of the alpha particles
3. Electrons are distributed around the nucleus and
occupy almost all the volume of the atom.

The nucleus is tiny compared with the atom as a
whole.
2. Structure of the Nuclear Atom
1.
Which of the following is NOT an example of a
subatomic particle?
A.
proton
B.
molecule
C.
electron
D.
neutron
2. Structure of the Nuclear Atom
2. The nucleus of an atom consists of
A.
electrons only.
B.
protons only.
C.
protons and neutrons.
D.
electrons and neutrons.
2. Structure of the Nuclear Atom
3. Most of the volume of the atom is occupied by the
A.
electrons.
B.
neutrons.
C.
protons and neutrons.
D.
protons.
Quiz Questions IN the Door
Review: What are three types of subatomic particles?
2. Explain: How does the Rutherford model describe
the structure of atoms?
3. Review: What are the charges and relative masses of
the three main subatomic particles.
4. Review: What were the 4 main ideas of Dalton’s
atomic theory?
1.
DATE: 11/11/2014
Bell-Ringer
List all the varieties of apples that you can think
of. Identify what is different about these apple
varieties.
3. Distinguishing Among Atoms
Connecting to Your World
 Just as apples come in different varieties, a chemical
element can come in different “varieties” called
isotopes.
3. Distinguishing Among Atoms
How can we tell elements apart?
 Recall:
 Atoms are composed of protons, neutrons, and electrons.
 Protons and neutrons make up the nucleus.
 Elements are different because they contain different
numbers of protons .
Atomic number – the number of protons in the nucleus
of an atom of that element.
 Specific to the identity of that element
 PEA
 Identify the necessary information in the table below.
Name
Symbol
Atomic Number
Protons
Electrons
Helium
27
Be
19
Tin
3. Distinguishing Among Atoms
How to determine the number of
neutrons.
Mass number – the total number of neutrons and
protons in an atom.
The number of neutrons in an atoms is the difference
between the mass number and atomic number.
Example: Lithium
Symbol
Atomic Number
Protons
Electrons
Mass number Neutrons
3. Distinguishing Among Atoms
 Identify the necessary information in the table below.
Name
Symbol
Atomic
Number
Protons
Electrons
Neon
Br
16
Lead
37
Ag
23
Mass
number
Neutrons
3. Distinguishing Among Atoms
Short hand Notation
 Short hand notation using mass
number and atomic number.
 Au is the chemical symbol for
Gold.
 Short hand can also be written
using the name and the mass
gold-197
Mass number
Atomic number
12
6
C
Chemical symbol
3. Distinguishing Among Atoms
 Identify the necessary information in the table below.
Short hand
Atomic
Number
Protons Electrons
10
6
31
Mass
number
Neutrons
3. Distinguishing Among Atoms
 Use your reference tables to express the composition of
each atom in shorthand form.
1. Nitrogen-14
5. Titanium-48
2.
Phosphorus-31
6. Yttrium-89
3.
Iodine-127
7. Tungsten-184
4. Osmium-190
8. Palladium-106
DATE: 11/12/2014
Bell-Ringer
 Write the word “neutron” 30 times. I am collecting
this.
BINGO NUMBERS
Question #1: 25
Question #2: 16
Question #3: 2
3. Distinguishing Among Atoms
Isotopes
How do isotopes of an element differ?
Isotopes - are atoms that have the same number of
protons but different numbers of neutrons.
Because isotopes of an element have different
numbers of neutrons, they also have different mass
numbers.
3. Distinguishing Among Atoms
Isotopes of Neon
 Comparing and Contrasting: How are these
isotopes different? How are they similar?
 Despite these differences, isotopes are chemically alike because they
have identical numbers of protons and electrons.
3. Distinguishing Among Atoms
Practice Problem
Writing Chemical Symbols of Isotopes
Diamonds are a naturally
occurring form of elemental
carbon. Two stable isotopes
of carbon are carbon-12 and
carbon-13. Write the symbol
for each isotope using
subscripts and superscripts to
represent the mass number
and the atomic number.
3. Distinguishing Among Atoms
Writing Chemical Symbols of Isotopes – Diamonds
1. Analyze: Identify the relevant concepts.


Isotopes are atoms that have the same number of
protons but different number of neutrons
Composition can be expressed by writing the
shorthand form with the chemical symbol, the atomic
number written as a subscript, and mass number as
superscript.
2. Solve: Apply the concepts to this problem.
 Symbol for carbon is ___
 The atomic number is ___
 The mass number for each isotope is given by its name
 Carbon-12 is
and Carbon-13 is
3. Distinguishing Among Atoms
Practice Problem
1.
Three isotopes of oxygen are oxygen-16, oxygen-17,
and oxygen-18. Write the symbol for each, including
the atomic number and mass number. Then identify
the number of protons, electrons, and neutrons for
each.
Name
Oxygen-16
Oxygen-17
Oxygen-18
Short hand
Protons
Neutrons
Electrons
3. Distinguishing Among Atoms
Practice Problem
2. Three isotopes of chromium are chromium-50,
chromium-52, and chromium-53. Write the symbol
for each, including the atomic number and mass
number. Then identify the number of protons,
electrons, and neutrons for each.
Name
Chromium-50
Chromium-52
Chromium-53
Short hand
Protons
Neutrons
Electrons
3. Distinguishing Among Atoms
Atomic Mass
How do you calculate the atomic mass of an
element?
 It is useful to compare the relative masses of atoms to a
standard reference isotope.
 Carbon-12 is the standard reference isotope. Cabon-12 has a
mass of exactly 12 atomic mass units.
 An atomic mass unit (amu) is defined as one twelfth of
the mass of a carbon-12 atom.
Example:
Helium-4 has a mass of 4.0026 amu: ≈1/3 the mass of a carbon-12
atom
Nickle-60 has a mass of 58.71 amu: ≈5 the mass of a carbon-12 atom
3. Distinguishing Among Atoms
Atomic Mass
 In nature, most elements occur as a mixture of two or
more isotopes.
 Each isotope has a fixed mass & natural percent
abundance.
 The atomic mass of an element is a weighted average
mass of the atoms in a naturally occurring sample of
the element.
3. Distinguishing Among Atoms
Weighted Average Mass of a Chlorine Atom
 Evaluating: How does a weighted average differ from
an arithmetic mean?
Some
Elements
and Their
Isotopes
3. Distinguishing Among Atoms
Using Atomic Mass to Determine the Relative
Abundance of Isotopes
The atomic mass of copper is 63.546 amu. Which of copper’s
two isotopes is more abundant: copper-63 or copper-65?
1. Analyze: Identify the relevant concepts.
• Atomic mass of an element is a weighted average
mass of the atoms in a naturally occurring element.
• Weighted average mass reflects both the mass and
the relative abundance of the isotopes as they occur
in nature.
2. Solve: Apply the concepts to this problem.
• The atomic mass of 63.546 amu is closer to 63 then
65. Because the atomic mass is a weighted average of
the isotopes, copper-63 must be more abundant than
copper-65
3. Distinguishing Among Atoms
Practice Problems
1.
Boron has two isotopes: boron-10 and boron-11.
Which is more abundant, given that the atomic mass
of boron is 10.81 amu?
2. There are three isotopes of silicon; they have mass
numbers of 28, 29, and 30. The atomic mass of
silicon is 28.086 amu. Comment on the relative
abundance of these three isotopes.
3. Distinguishing Among Atoms
Atomic Mass
How do you calculate the atomic mass of an
element?
 To calculate the atomic mass of an element, multiply
the mass of each isotope by its natural abundance,
expressed as a decimal, and then add the products.
Example: carbon has two stable isotopes:


Carbon-12, which has a natural abundance of 98.89%, and
Carbon-13, which has a natural abundance of 1.11%.
3. Distinguishing Among Atoms
Calculating Atomic Mass
Element X has two natural isotopes. The isotope with a
mass of 10.012 amu (10X) has a relative abundance of
19.91%. The isotope with a mass of 11.009 amu (11X) has
a relative abundance of 80.09%. Calculate the atomic
mass of this element.
3. Distinguishing Among Atoms
Practice Problems
1.
The element copper has naturally occurring isotopes with
mass numbers of 63 and 65. The relative abundance and
atomic masses are 69.2% for mass = 62.93 amu, and
30.8% for mass = 64.93 amu. Calculate the average
atomic mass of copper.
63.6 amu
2.
Calculate the atomic mass of bromine. The two isotopes
of bromine have atomic masses and relative abundance of
78.92 amu (50.69%) and 80.92 amu (49.31%).
79.91 amu
3. Distinguishing Among Atoms
Practice Problems
3. Chlorine has two isotopes, chlorine-35 (atomic mass
34.97 amu, relative abundance 75.77%) and chlorine37 (atomic mass 36.97 amu, relative abundance
24.23%). Calculate the atomic mass of chlorine.
35.45 amu
3. Distinguishing Among Atoms
The Periodic Table – A Preview
Why is a periodic table useful?
A periodic table is an arrangement of elements in
which the elements are separated into groups based on
a set of repeating properties.
A periodic table allows you to easily compare the
properties of one element (or a group of
elements) to another element (or group of
elements).
3. Distinguishing Among Atoms
The Periodic Table
3. Distinguishing Among Atoms
The Periodic Table
Period – each horizontal row of the periodic table
 Within a given period, the properties of the elements
vary as you move across it from element to element.
 There are 7 periods in the modern P.T.
Group or Family – each vertical column of the periodic
table.
 Groups are identified by a number and a letter.
 Elements within a group have similar chemical and
physical properties.
3. Distinguishing Among Atoms
A Period
3. Distinguishing Among Atoms
A Group or Family
3. Distinguishing Among Atoms
1. Isotopes of an element have
A.
the same mass number.
B.
different atomic numbers.
C.
the same number of protons but different
numbers of neutrons.
D.
the same number of protons but different
numbers of electrons.
3. Distinguishing Among Atoms
1. How many neutrons are in sulfur-33?
A.
16 neutrons
B.
33 neutrons
C.
17 neutrons
D.
32.06 neutrons
3. Distinguishing Among Atoms
1. If sulfur contained 90.0% sulfur-32 and 10.0% sulfur-
34, its atomic mass would be
A.
32.2 amu.
B.
32.4 amu.
C.
33.0 amu.
D.
35.4 amu.