Matter and Environment:
ENVIRONMENT
PERIODIC TRENDS
PERIODIC TRENDS
INDICATORS
A periodic trend is an indicator of how elements’ properties
change as you move across the periodic table.
ELEMENT PROPERTIES
FOUR DIFFERENT
We will study four different properties and their organization
within the periodic table:
1.
Atomic size
2.
Ionization energy
3.
Electronegativity
4.
Reactivity
ATOMIC SIZE (aka ATOMIC RADIUS)
ATOMIC SIZE
RADIUS
Atomic size refers to the distance
from an atom’s nucleus to its
valence shell. (the highest energy
level)
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ATOMIC SIZE
RADIUS
Atomic size increases as you move down a group because there
are more energy levels
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ATOMIC SIZE
RADIUS
Atomic size increases as you move left on the
periodic table because there are fewer protons
pulling on the electrons.
*SHIELDING EFFECT - the more energy levels
you have, the less protons “pull” on electrons
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ATOMIC SIZE
RADIUS
So basically… atomic size increases as you move down and as you move left.
ATOMIC SIZE
RADIUS
IONIZATION ENERGY
ION REMOVAL
Ionization energy is the energy necessary to
remove an electron from a neutral atom, starting
from the last energy level (valence shell).
LOW IONIZATION ENERGY = it is easy to remove
electrons = elements are MORE LIKELY TO BECOME
CATIONS
HIGH IONIZATION ENERGY = it is difficult to
remove electrons = elements are MORE LIKELY
TO BECOME ANIONS.
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IONIZATION ENERGY
ION REMOVAL
Ionization energy increases as you move up a group because there are
less energy levels “shielding” the electrons from the protons’ “pull”
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IONIZATION ENERGY
ION REMOVAL
Ionization energy increases as you move left across a period because
there are more protons and so the positive charge increases.
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IONIZATION ENERGY
ION REMOVAL
So basically… ionization energy increases as you move up and as you move right.
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IONIZATION ENERGY
ION REMOVAL
ELECTRONEGATIVITY
ATTRACTION
Electronegativity is a measure of how
easy it is to attract and retain electrons in
an atom when it forms a chemical bond.
LOW ELECTRONEGATIVITY = it is difficult for an
element to attract electrons (easy to let them go);
elements are MORE LIKELY TO BECOME CATIONS
HIGH ELECTRONEGATIVITY = it is easy for an
element to attract electrons; elements are MORE
LIKELY TO BECOME ANIONS.
Ca+ion
Anion-
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ELECTRONEGATIVITY
ATTRACTION
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Noble Gases are
stable or “inert”
so they do not
attract electrons,
thus
Electronegativity
equals zero (0)
Electronegativity increases as you move up a group because there are
less energy levels “shielding” the electrons from the protons’ “pull”
ELECTRONEGATIVITY
ATTRACTION
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Noble Gases are
stable or “inert”
so they do not
attract electrons,
thus
Electronegativity
equals zero (0)
Electronegativity increases as you move right across a period because elements have more
electrons, (i.e. elements’ valence shells are more than half full, so it is easier to attract electrons
than to lose them).
ELECTRONEGATIVITY
ATTRACTION
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Noble Gases are
stable or “inert”
so they do not
attract electrons,
thus
Electronegativity
equals zero (0)
So basically… electronegativity increases as you move up and as you move right.
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REACTIVITY
ATTRACTION
Elements that are reactive are those
that easily form bonds with other
elements to form compounds.
Having an incomplete valence
shell, (i.e. electrons still ‘fit’ into the
last energy level).
REACTIVITY IN METALS
ATTRACTION
Metals react more easily the farther left and farther down they
are in the periodic table.
FARTHER LEFT = fewer electrons
FARTHER DOWN = more energy levels = farther away from nucleus =
weaker “pull” from protons
REACTIVITY IN METALS
ATTRACTION
1
1
18
2
M E TA L S
2
3
4
5
6
7
3
4
5
6
7
8
9 10 11 12
13 14 15 16 17
REACTIVITY IN NON-METALS
ATTRACTION
Nonmetals react more easily the farther right and farther up
they are in the periodic table.
FARTHER RIGHT = more electrons = fewer “spots to fill”
FARTHER UP = fewer energy levels = closer to nucleus = stronger
“pull” from protons
REACTIVITY IN METALS
ATTRACTION
1
1
18
2
13 14 15 16 17
N O N - M E TA L S
2
3
4
5
6
7
3
4
5
6
7
8
9 10 11 12
Metal Reactivity Increases
REACTIVITY
ATTRACTION
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Non-Metal Reactivity Increases
TO RECAP
SO, BASICALLY…
THIS
%
egativity
egativity
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ONE LAST THING
THE OCTET (8) RULE
THE PERFECT BALANCE
All atoms (except Hydrogen) want to have 8 electrons in their
outermost energy level (valence shell)
Noble gases have 8 electrons in their valence shell. This is why they are
so stable and unreactive.
Atoms with few (<4) valence electrons will lose them when forming
bonds.
Atoms with many (>5) valence electrons will gain electrons
THE OCTET (8) RULE
IN ACTION
Atoms with few (<4) valence electrons will lose them when
forming bonds.
Atoms with many (>5) valence electrons will gain electrons
Example: NaCl
END OF PRESENTATION