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SCIENCE 10 SUPPORT
Shell Diagrams
SIMILAR CHEMICAL PROPERTIES
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The reason for similar properties has do do with
electrons.
We are able to predict the kinds of compounds
that metals and non-metals are able to form.
Different elements have different numbers of
electrons.
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ATOM DIAGRAM
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NIELS BOHR (1885-1962)
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Student of Rutherford
Proposed that electrons are arranged in a
concentric circular paths, or orbits, around the
nucleus.
nucleus
Sometimes called the planetary model.
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BOHR-RUTHERFORD MODEL
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Electrons in a particular path have a fixed
energy.
This means they do not lose energy and fall into
the nucleus.
nucleus
The orbit that the electrons travel are displayed
by lines around the nucleus.
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SHELLS
Shells are what electrons move around the
nucleus “on.”
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ELECTRON SHELLS
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ELECTRON SHELL PATTERNS
1.
Period 1 elements have a single electron shell,
while Period 2 elements have two electron shells
and Period 3 elements have 3 electron shells.
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2.
Elements in the same group have the same
number of electrons in their outermost shell.
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PREDICTING CHEMICAL REACTIVITY
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Electron shell diagrams are useful because they
show the number of electrons in the outer shells.
Knowing this is the key to understanding the
organization of the periodic table and the
chemical properties of elements.
Elements in the same group have similar
chemical properties because they have the same
number of electrons in their outer shell.
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DRAWING BOHR-RUTHERFORD MODEL
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Steps
1. A circle is drawn to represent the nucleus of an
atom. Within this circle we write how many
protons and neutrons are in the atom.
atom
2. The next thing is to draw electron orbits
around the nucleus. The number of orbits
depends on how many electrons an atom has.
3. “Dots” drawn on the orbits represent electrons.
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RULES CONTINUED
4. The first shell (closest to the nucleus) can
contain a max of 2 electrons.
5. The second shell can contain a maximum of 8
electrons (octet).
(octet)
6. The third shell will only contain a max of 8 (for
us)
7. The fourth shell will only contain a max of 2 (for
us)
RULES CONTINUED
8. When placing electrons, put them opposite or
furthest away from each other as possible (think
magnets).
9 Electrons placed in shells 2 or 3 should be
9.
written one at a time and then paired.
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EXAMPLE
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How many electrons does potassium contain?
Sketch a shell diagram for potassium.
Potassium has an atomic number of 19;
y
It has 9 electrons
EXAMPLE 2
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1.
2.
3.
4.
Sketch a shell diagram for:
Neon
Chlorine
Carbon
Helium.
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FAMILIES WITHIN THE PERIODIC TABLE
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VALENCE ELECTRONS
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The outer shell is called the valence shell
and the electrons that occupy it are called
valence electrons.
A chemical bond forms between two atoms when
their valence electrons form a stable
arrangement together.
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VALENCE ELECTRONS
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Metals are elements that tend to lose their
valence electrons relatively easily and this
accounts for many of their physical and chemical
properties.
Metals tend to lose valence electrons while nonmetals tend to gain them.
One important property of valence shells is that
they generally like to be full.
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