Electronics
The Nature of Matter
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Presentation Overview
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Terms and Definitions
Atom Models
Electrons and Electron Shells
Random Drift of Electrons
Law of Electrical Charges
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Terms and Definitions
A.
B.
C.
D.
E.
Matter- A material substance that occupies space
and has mass; can be solid, liquid, or gas
Atom- A basic unit of matter consisting of a dense
nucleus surrounded by a cloud of electrons
Element- Matter composed of atoms having the
same number of protons in the nucleus
Compound- Substance consisting of two or more
elements joined by chemical bonds
Molecule- Stable combination of two or more
atoms
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Terms and Definitions (continued)
F.
G.
H.
I.
J.
K.
Mixture- A substance made by combining two or
more materials that are not joined chemically
Charge- A basic property of matter
Electron- A subatomic particle with a negative
electric charge
Proton- Positively charged subatomic particle—
generally located in the nucleus
Neutron- Subatomic particle with no charge—
generally located in the nucleus
Ion- An electrically charged atom where the
number of protons does not equal the number of
electrons
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Atoms
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Fundamental units of matter.
Consists of a nucleus having at least one proton and
usually one or more neutrons, with a number of
electrons bound to the nucleus through electrical
attraction.
Atoms are the simplest forms of an element that still
have the unique characteristics of that element.
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Atomic Particles
Classical image
Bohr model
Modern image
Cloud model
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Elements and Compounds
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Matter is anything that occupies space or has mass.
An element is a substance consisting of atoms that
have the same number of protons in the nucleus.
Compounds are mixtures or combinations of two or
more elements.
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How Does This Relate to
Electricity?
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Electricity and electronics relates to the behavior of
electrons.
Electricity relates to the buildup and flow of
electrons.
Electronics relates to the control of electricity by
specialized devices.
 Transistors and integrated circuits
To understand electricity and electronics, we need to
understand more about electrons.
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Electrons
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Electrons orbit the nucleus of an atom.
The total number of electrons is generally equal to
the number of protons.
Electrons arrange themselves into layers.
These layers are called shells or orbitals.
Each shell contains one or more electrons.
The number of electrons in each shell follows a
formula Ne = 2n2.
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Inner and Outer Orbits
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When these are inner orbits of an atom, they contain
electrons up to their maximum count and contain no
free electrons.
 Orbit #1- can contain two electrons maximum
 Orbit #2- can contain eight electrons maximum
 Orbit #3- can contain 18 electrons maximum
The maximum number of electrons in the outer orbit
is eight.
The outer orbit of the atom is an orbit that may be
partially filled or contain free electrons.
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Electron Shells
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Electrons are attracted to protons.
Electrons in inner shells are closer to the nucleus.
 Electrons in inner shells have low energy.
 Electrons in outer shells have more energy.
Inner shell electrons are strongly attracted to the
nucleus.
 These electrons are considered bound.
 They never gain enough energy to leave the atom.
 They are never shared between atoms.
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Valence Electrons
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Only outer shell electrons are important to electricity
and chemistry.
 They can be shared and form bonds.
The outer shell is called the valence shell.
 Electrons in this shell are called valence electrons.
Electrons in the outer shell can gain enough energy to
completely leave the atom.
 These electrons become free.
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Free Electrons
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Free electrons are important to electricity.
 They can move and be used to build up charge or
create current.
Materials without free electrons cannot create or
conduct electricity.
 These materials can be insulators.
The best conductors are those with only one
electron in the outer shell.
 Gold, silver, copper
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Periodic Table of the Elements
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The Periodic Table of the Elements is arranged by
atomic number.
The atomic number of an element refers to the
number of protons that make up an atom of the
element.
 The number of electrons generally equals the
number of protons.
Groups of elements read in a vertical column up and
down.
Elements in a group have the same number of outer
shell electrons.
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Periodic Table of the Elements
(continued)
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Reading across in a row, the number of protons
in the nucleus increases by one.
Because the number of electrons in an atom is
generally equal to the number of protons, different
elements can have different numbers of electrons in
their valence shell.
 Atoms without the same number of electrons and
protons can exist and are called ions.
Elements with the same number of valence electrons
are similar electrically and chemically.
 They can be grouped together.
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Free Electrons
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Electrons are bound to the nucleus because of
electrostatic forces of attraction between positive
protons in the nucleus and negative electrons
orbiting the nucleus.
Inner shell electrons are strongly bound.
The outer shell electrons in conductors are weakly
bound.
 Room temperature heat energy is enough to allow
them to become free electrons.
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Conductors
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Good conductors generally have one or two
electrons in the outer shell.
 Aluminum is a good conductor with three
electrons in its outer shell.
The number of inner shell electrons nearly balances
the number of protons.
 This creates a charge layer that shields the outer
shell electrons.
 They do not feel the same attraction force the
inner electrons do.
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Metals
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Metals are good conductors because they
generally have two electrons in the outer shell.
 Metals start with Row 4.
Going across the row, each element has one additional
proton in the nucleus.
Each additional electron needed to balance the charge
goes into an inner shell.
 Atoms can only have more than eight electrons in a
shell for an inner shell.
 The number of outer shell electrons stays at two.
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Row 4 Metals
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Row 4 means four layers (shells) of electrons.
The number of electrons in each shell follows the
formula- Ne = 2n2.
The third layer can have 18 electrons.
But, the outer shell of an atom can only have a
maximum of eight electrons.
We only start to get more than eight electrons in the
third shell after an atom has a fourth shell.
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Electron
Shells
Nucleus
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Shell
Number
4
3
2
1
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Maximum number
of electrons in each
shell.
32
18
8
2
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32 electrons in
the fourth
shell.
32
18
8
2
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But only eight
electrons if any
shell is the outer
shell.
8
18
8
2
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The third shell can
only have eight
electrons if it is an
outer shell.
8
8
2
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It can have 18
electrons only
when there
is a fourth
shell.
2
18
8
2
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Good Conductors
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Note the column that has Cu, Ag, and Au.
 Copper, silver, gold
Each of these metals has one electron in its
outer shell.
Other metals in each row have two electrons in the
outer shell.
This is because atoms are more stable when each
electron shell is “full.”
 Consider the inert gasses.
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Copper
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Copper is the first element to be able to have a full
third shell with 18 electrons.
Remember there must be a fourth shell to be able to
get 18 electrons in the third shell.
Copper has the following number of electrons in
each shell: 1, 2; 2,8; 3,18; 4,1 Key: shell, # of electrons
2 + 8 + 18 + 1 = 29, which is the atomic number for
copper.
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Slides 32-40 are pictures showing
the electrons in each shell from
atomic numbers 19 to 31.
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Potassium (K)
1
19 electrons
8
8
2
19 protons
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Calcium (Ca)
2
20 electrons
8
8
2
20 protons
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Scandium (Sc)
2
21 electrons
The next electron
goes into the
third shell.
9
8
2
21 protons
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Skip from Scandium to Nickel. Each extra electron goes into the third shell.
Nickel (Ni)
2
28 electrons
The next electron
goes into the
third shell.
16
8
2
28 protons
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Copper (Cu)
1
29 electrons
18
8
2
29 protons
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Copper (Cu)
1
29 electrons
18
8
2
One outer shell
electron.
29 protons
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Copper (Cu)
1
29 electrons
18
8
2
Note this full
third shell.
29 protons
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Zink (Zn)
2
30 electrons
18
8
2
30 protons
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Gallium (Ga)
3
31 electrons
18
8
2
31 protons
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Presentation Summary





Terms and Definitions
Atom Models
Electrons and Electron Shells
Random Drift of Electrons
Law of Electrical Charges
Copyright © Texas Education Agency, 2013. All rights reserved.
41