Download Atomic Theory, and the Periodic Table

Atomic Theory and the
Periodic Table
Fall 2014
ATOMS & THE PERIODIC TABLE
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1. An atom is the
smallest particle of an
element.
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It has a positively charged
nucleus surrounded by
negatively charged
electrons.
2. The nucleus is the tiny
positive core of the atom
which contains most of the
mass of the atom.
ATOMS & THE PERIODIC TABLE
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The proton is the positively
charged particle found in the
nucleus of the atom. It has a
mass of 1 a.m.u.
The neutron is the particle
with no charge is found in the
nucleus of the atom. It has a
mass of 1 a.m.u.
The electron is the negatively
charged particle found in the
electron cloud outside of the
nucleus. It is so very small
that the mass is ignored.
ATOMS & THE PERIODIC TABLE
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3. One atomic mass unit
(amu) is defined as onetwelfth the mass of a carbon12 atom.
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The atomic mass is the mass of
an atom in relation to the carbon12 atom.
4. The number of protons in
the nucleus of an atom of an
element is the atomic number
of the element.
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Mass number is the sum of the
protons and neutrons in an atom.
The number of neutrons can be
found by subtracting the atomic
number from the mass number.
Quarks- all atomic particles
are made up of even smaller
particles called quarks. The
arrangement of the quarks
decides what atomic particle
is formed. There are five
known quarks.
ATOMS & THE PERIODIC TABLE
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5. Scientists have developed a
language of symbols to stand for the
elements.
A chemical symbol is a notation of
one, two or three letters that represent
an element.
 The first letter of each symbol is a
capitol letter. If a second letter is used,
it is always a lower-case letter.
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ATOMS AND THE PERIODIC TABLE
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6. Scientists use models to
explain something that they
cannot see or understand by
relating it to something that
they do see or understand.
ATOMS & THE PERIODIC TABLE
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7. The main points of Dalton’s atomic
theory can be stated as follows:
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All matter is made up of tiny particles called
atoms that cannot be split into smaller
particles.
Atoms cannot be created or destroyed.
All atoms of the same element have the same
properties, and the atoms of different
elements have different properties.
Atoms of different elements can combine to
form new substances.
Atom and Periodic Table
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8. J.J. Thompson was an English
scientist. He discovered the electron when
he was experimenting with gas discharge
tubes. He noticed a movement in a tube.
He called the movement cathode rays.
The rays moved from the negative end of
the tube to the positive end. He realized
that the rays were rays were made of
negatively charged particles – electrons.
ATOMS & THE PERIODIC TABLE
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9. Rutherford, through experimentation,
theorized that the atom contained a small,
dense, positive core.
10.In 1913, Bohr developed a model of
the atom where electrons move in paths.
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Each path is a certain distance from the
nucleus.
The paths in which electrons circle the
nucleus are called energy levels.
Electrons in each energy level have a definite
amount of energy.
ATOMS & THE PERIODIC TABLE
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10. In 1926, Erwin Schrodinger proposed the electron
cloud model. These regions of space containing the
electrons are called electron clouds.
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11. The modern Periodic Table was first organized by
Dimitri Mendeleev by arranging elements in order of
increasing atomic mass. By listing the elements
according to their mass, Mendeleev found that there was
a repeating pattern.
Today’s Periodic Table is now based on the
element’s atomic number.
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ATOMS & THE PERIODIC TABLE
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12. In the Bohr model of an atom, the small circle
represents the nucleus. The p+ stands for protons, and
the n0, neutrons. The circles around the nucleus
represent the energy levels. The e- stands for electrons
and their negative charge.
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Bohr Diagram
ATOMS & THE PERIODIC TABLE
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13. Each energy level can hold a certain number
of electrons.
Energy Level 1
2e-
Energy Level 2
8 e-
Energy Level 3
18 e-
Energy Level 4
32 e-
ATOMS & THE PERIODIC TABLE
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14. If the atoms is neutral, the number of
protons equals the number of electrons.
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An atom with a charge is called an ion. An
atom becomes charged by gaining OR losing
electrons.
Atoms of the same element with different
numbers of neutrons are called isotopes.
15.Valence electrons are the electrons in
the outer energy level of an atom. No
atom has more than eight electrons in its
outer level.
ATOMS & THE PERIODIC TABLE
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16.A nuclear reaction is a reaction
change in the atom’s nucleus.
17.Types of nuclear reactions:
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nuclear fission – the process of splitting a
nucleus into two nuclei with smaller masses.
nuclear fusion – the process caused by the
fusing together of nuclei.
18.Certain identified isotopes, such as
tracers, are used in nuclear medicine.
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Tracers are radioisotopes that are used
inside of a body to monitor body processes.
ATOMS & THE PERIODIC TABLE
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19.A. METALS:
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1.Metals donate electrons.
2. Located on the left hand side of the zigzag line
of the Periodic Table.
3.Metallic properties:
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a. Luster
b. Ductile - May be drawn into wire.
c. Malleable - Can be hammered into thin sheets.
d. Good conductors of heat and electricity.
e. Tend to give up electrons in making bonds.
f. Can be identified by spectral analysis techniqueswhen materials give off excess energy in the form of
different colors of light
ATOMS & THE PERIODIC TABLE
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B. NONMETALS:
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1. Nonmetals gain electrons.
2. Located on the right side of the zig-zag line of the
Periodic Table (except column 18 or 8A)
3. Nonmetallic properties:
 a. Brittle
 b. Good insulators
 c. Tend to take in electrons in making bonds.
C. NOBLE GASES:
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1. Also called "inert gases".
2. Located in Group 18.
3. Rarely react ( the outer energy level is full).
ATOMS & THE PERIODIC TABLE
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D.TRANSITION ELEMENTS:
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1. Special metals are in Groups 3-12. (all B
metals)
2. Properties:
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a. Can be magnetized.
b. Strong characteristic colors.
E. METALLOIDS :
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1. Special elements identified as B, Si, Ge,
As, Sb, Te, Po and At.
2. Properties: Metalloids have properties of
both metals and nonmetals.
ATOMS & THE PERIODIC TABLE
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20. The Periodic Table is organized by
periods and groups or families.
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Periods define all elements in a horizontal
row.
Groups or Families define all elements in a
vertical column.
21.All elements in the same group or
family have the same number of valence
electrons.
22.All elements in the same period have
the same number of energy levels.