Transcript Properties of Atoms and the Periodic Table

Chapter 19 – Properties of
Atoms & the Periodic Table
Chapter preview
sections
1 Structure of the Atom
2 Masses of Atoms
3 The Periodic Table
Atoms Compose All Things, Great and Small
Everything in the universe is composed of tiny
particles called atoms. You will learn about atoms
and their components:
protons, neutrons, electrons, and quarks.
Properties of Atoms and
the Periodic Table
Section 1—Structure of the
Atom
Original Author: Donna Myers
Scientific Shorthand

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Elements are abbreviated in scientific
shorthand.
Consist of one capital letter or a
capital letter plus one or two small
letters.
Some symbols are derived from Latin.
• Argentum is Latin for “silver”
Learn Table 1 on page 578
Symbols of Some Elements
Element Symbol
Element
Symbol Element Symbol
Aluminum
Al
Gold
Au
Mercury
Hg
Calcium
Ca
Helium
He
Nitrogen
N
Carbon
C
Hydrogen
H
Oxygen
O
Chlorine
Cl
Iodine
I
Potassium K
Copper
Cu
Iron
Fe
Silver
Ag
Fluorine
F
Magnesium Mg
Sodium
Na
Atom

An element is matter
that is composed of
one type of atom.


Atom is the smallest
piece of matter that
still has the
properties of the
element.
A chemical symbol
represents the name
of an element.
Atomic Components
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Protons—particles
with electrical
charge of 1+
Neutrons—neutral
particles with no
electrical charge.
Electrons—
particles with
electrical charge of
1–
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Nucleus—
positively charged
central core of the
atom
Atomic components
•
•
Protons and
neutrons are in
center of nucleus.
The region around
the nucleus
occupied by
electrons is called
the electron cloud.
Quarks
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The nucleus of the atom
contains protons and
neutrons that are
composed of particles of
matter called quarks.
Six quarks are known to
exist.

Bubble chamber image
Quarks are studied by
colliding accelerated
charged particles with
protons, which leave
tracks in a bubble
chamber.
Bubble chamber
Tevatron

A tevatron is used to
accelerate protons in
the study of
subatomic particles.
Models

Scientists use
scale-up models to
represent atoms.

John Dalton’s
atomic model was a
simple sphere.
NATIONAL
Visualizing the
GEOGRAPHIC Atomic Model
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The ancient Greek philosopher Democritis
proposed that elements consist of tiny,
solid particles that cannot be subdivided.
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Democritis’s Uncuttable Atom
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Rutherford Model, 1911
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Thompson Model, 1904
See Figure 5, page 582
Bohr Model, 1913
The Electron Cloud Model
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(Current)
In 1926, scientists developed the electron cloud
model of the atom that is used today.
This model shows electrons traveling in specific
energy levels around a nucleus of protons and
neutrons.
According to present atomic theory, the location of
an electron in an atom cannot be pinpointed
exactly.
Masses of Atoms
Section 2
Atomic Mass
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Composed mostly
of protons and
neutrons.
Majority of the
mass of an atom is
located in the
nucleus.
Atomic Mass Units
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Unit of measurement
for atomic particles is
atomic mass unit
(amu) which is onetwelfth the mass of a
carbon atom
containing six protons
and six neutrons.
1 amu = mass of 1
proton or 1 neutron
Comparison of Particles in an
Atom
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Protons and neutrons are about the
same size and mass.
Electrons are about 1,836 times
smaller than protons and neutrons.
Atomic Number

Protons identify the
element.
Mass Number
 The
sum of the number of
protons and neutrons in an
atom
• Protons + neutrons = mass number
• A certain atom has 26 protons, 26
electrons, and 30 neutrons. What is
its mass number?
Mass Numbers of Some Atoms (page 585)
Element
Symbol
Atomic
Number
Protons
Neutrons Mass
Number
Average
Atomic
Mass
Boron
B
5
5
6
11
10.81
Carbon
C
6
6
6
12
12.01
Oxygen
O
8
8
8
16
16.00
Sodium
Na
11
11
12
23
22.99
Copper
Cu
29
29
34
63
63.55
Isotopes
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Atoms of the same element with different
numbers of neutrons.
Different isotopes have different properties.
Name of element followed by mass number
identifies the isotope.
•
•
•
Carbon-12
Carbon-14
Lead-206
Isotopes
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To find number of neutrons:
•
mass number – atomic number =
number of neutrons
Atoms of boron have mass numbers of
10 or 11. How many neutrons are in a
boron atom?
• Boron-10
• Boron-11
10 – 5 = 5 neutrons
11 – 5 = 6 neutrons
Average Atomic Mass
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The average atomic mass is the weightedaverage mass of the mixture of its isotopes.
Average atomic mass is closest to its most
abundant isotope.
Four out of five atoms of boron are boron11 and one out of five is boron-10
Average atomic mass of boron is close to mass of
most abundant isotope, boron-11.
Isotopes
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The average mass is closest to its most
abundant isotope
• Chlorine’s atomic mass is 35.453.
possible isotopes of chlorine.
• Cl-35 and Cl-36
List two
1) Use paper and pencil (colored if you have them) to draw
the electron cloud model for lithium. Include the correct
number of protons and electrons. Include four neutrons in the
drawing.
2) Calculate the weighted average of the following quiz
scores: 5 students scored 80%; 19 students scored 90%.
Work Section 2
Assessment, page 587
The Periodic Table
Section 3
Periodic Table
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The modern day
periodic table is a
chart showing the
classifications
of
elements according
to their properties
and
increasing
atomic numbers.
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The p. t. is useful
because it shows the
relationship among
the elements and it
can be used to
predict
similarities
and
differences
among the elements.
Dmitri Mendeleev
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Developed the first periodic table
He arranged the elements by increasing
atomic mass and aligned them in
columns based on chemical and physical
properties.
Groups On The Periodic Table
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Elements arranged in vertical columns in
the periodic table
Elements in a group have similar
properties
Elements in a group have the same
number of electrons in their outer energy
level.
There are 18 groups
Energy Levels
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There are 7 energy levels
Energy level one contains a maximum of
2 electrons
Maximum number of electrons in
second energy level is 8.
Each row in the periodic table ends
when an outer energy level is filled.
Major energy level
K
L
M
N
O
P
Q
Maximum number
of electrons
2
8
18
32
32
18
2
Noble Gases
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Group 8A on periodic table
A complete and very stable electron
arrangement in the outer energy level
will contain 8 electrons—this very
stable arrangement is characteristic
of noble gases.
Electron Dot Diagrams
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Are used to show how electrons in the
outer energy level are bonded when
elements combine to form compounds.
Periods
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Horizontal rows of elements that contain
increasing numbers of protons and
electrons.
One proton and one electron are added
to each element as you go across the
periodic table from left to right.
Classification of Elements
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All elements in yellow squares are metals.
All elements in green squares are nonmetals
All elements in purple squares are metalloids or
semimetal.
Properties of Metals
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Most metals exist as
solids at room
temperature
They are shiny, can
be drawn into wires,
pounded into sheets,
and are good
conductors of
electricity.
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Moving from left to
right in a row of the
periodic table,
metallic properties of
atoms decrease.
Properties of Nonmetals and
Metalloids
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Nonmetals—
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•
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Most are gases
Brittle
Poor conductors of
heat and electricity
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Metalloids
•
Have some properties
of both metals and
nonmetals
Chlorine gas
Boron and silicon
Elements in the Universe
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All elements
throughout the
universe are the same.
Hydrogen and helium
are the building blocks
of other naturally
occurring elements.
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Scientist believe that
naturally occurring
elements are
manufactured within
stars.