Transcript Periodic Trends

IONIZATION
ENERGY
Ionization energy:
The energy required to remove an
electron from an gaseous atom or an
ion. Measure in Joules.
Think of it as a measure of how strongly
an atom holds onto its electrons. The
more energy required to remove it, the
greater hold the nucleus had on it.
Trend:
Ionization energy increases across a period
This is due to increase of nuclear charge
and decreasing radii. (it is harder to
remove an electron)
Ionization energy decreases down a group
This is due to increasing radii and
decreasing nuclear charge. ( it is easier to
remove an electron.
Ionization Energy Trend
Kent. "KentChemistry Movie Page." Mr. Kent's Chemistry Regents Help and AP
Chemistry Exam Review Pages. Web. 25 Oct. 2010.
<http://www.kentchemistry.com/moviesfiles/movieindex.htm>.
Review Questions
What is ionization energy?
1.
1.
1.
2.
3.
4.
The energy required to remove one
electron from neutral atom of an element.
The energy that occurs when an atom is
added to a negative ion.
An ion’s energy that is required to move a
neutral atom out of the nucleus
The energy required to add one electron
to the neutral atom of an element.
Review Questions
2.
2. What trend does ionization energy
have?
1.
2.
3.
4.
Decrease across a period and decreases
down a group.
Increase across the period and decrease
down a group.
Increase across a period and increases
down a group.
Decrease across the period and increases
down a group.
Review Questions
What group has the lowest Ionization
Energy?
a) D- block
b) Group 17 Halogens
c) Group 18 Noble Gas
d) Group 1 Metals
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d
Review Questions
What is responsible for increasing
Ionization Energy?
a) Increasing Nuclear Charge
b) Decreasing Nuclear Charge
c) Increase Electron Affinity
d) Increase Ionic Radii
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a.
Review Questions
What is the label for Ionization Energy?
a) Ions
b) Mole
c) kJ or J
d) kJ/mol
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c.
Electron Affinity
Definition:
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Electron Affinity: “The energy
change that occurs when an
electron is acquired by an neutral
atom.” (Modern Chemistry, p 157)
The energy change is negative (which means that
energy is released).
The more energy that is released, the more
negative the number.
Trends of Electron Affinity:

Trend across:
Increases
2. Why? The elements want to gain more
electrons because the elements want to
get a full orbital.
Trend down:
1. Either decreases or stays the same
2. Why? A slight increases the nuclear charge
and increase in atomic radius.
1.
Period Trend
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The electron affinity increases as you
go across the periods because elements
want to gain electrons to reach stable
configuration as you go to the right.
Group Trend

The electron affinity decreases as you
go down in the columns because it gets
more difficult to add electrons to an
atom that already has many that are
further from the nucleus.
Pictures:
Review Questions:
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1. What is electron affinity?
The energy change that occurs when
an electron is acquired by an neutral
atom.
2. What is the trend across for electron affinity?
Increases
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3. What is the trend down?
Either decreases or stays the same
4. Which element is higher: Potassium or
Bromine
Bromine (-336.5)
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5. Which element is lower: Oxygen or Polonium?
Oxygen(-146.1)
6. Why are the numbers negative?
The quantity of energy absorbed would be
represented by a positive number, but the energy
released would be represented by a negative
number. If more energy releases a higher number
occurs. The negative is just the lose of energy.
Electronegativity
Electronegativity
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“A measure of the ability of an atom
in a chemical compound to attract
electrons from another atom in the
compound” (Modern Chemistry).
The better they are at attracting
electrons, the higher the number.
Subtracting the electronegativities of
two elements, indicates the type of
bond that they would form.
trend
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Electronegativites
generally increase
from left to right
across the period.
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The energy levels
want 8 electrons.
Energy levels fill up
making them more
capable of attracting
electrons from
another atom.
trend
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Electronegativites will generally
decrease down a group or stay about
the same.
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Because of the ending sublevel of p6 .
why?
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Every element wants to fill its entire
energy level up to p6 .
As atoms get closer to having eight
electrons in an energy level, they
attract electrons more strongly. (s2 ,p6 )
Range of electronegativity
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Lowest:0.7 (Francium)
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Highest: 4 (Fluorine)
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Range: 0.7-4
http://periodictable.com/Elements/087/index.html
Range of electronegativity
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Unit: no unit it is more like a ranking.
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Subtracting electrongativities will predict
the type of bond
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Covalent (difference of 0-0.3)
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Polar covalent (difference of 0.3-1.7)
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Share electrons
Share electrons unevenly
Ionic (difference of greater than 1.7)
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Transfer electrons
Review Questions
1.
2.
3.
What is the most electronegative
element on the periodic table?
Fluorine
What is the range of electronegativity?
0.7-4
As you go across a period, do the
levels of electronegativity increase? Or
decrease? Increase
Review questions
4.
5.
6
What is the least electronegative
element in the periodic table?
Francium
What is the sublevel every atom wants
6
p
to be at?
What scale is electronegativity
measured by?
Pauling scale (a scale
that ranks)
Atomic Radius
Definition
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“Half the distance between identical
atoms that are bonded together.”
(Modern Chemistry)
Half the distance between metal ions
that are next to each other.
Measured distance of pm (picometers)
Trend Going down
Atomic Radius increases down a family.
The number of valence electrons remains
the same
The trend in larger atoms going down a
group is due to adding electrons to
subsequent energy levels.
Trend Going Across
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The atomic radius decreases across a
period.
“The trend to smaller atoms across the
period is caused by the increasing
positive charge of the nucleus.”
(Modern Chemistry)
Why does it Occur
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“The trend to smaller atoms across the
period is caused by the increasing
positive charge of the nucleus.”
(Modern Chemistry)
Unit
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Atomic Radius is measured in
picometers (pm) (Modern Chemistry)
Smallest Elements
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Neon with 38pm, and Hydrogen with
25pm them two are the smallest in
atomic radius. And is always positive
and never negative.
Largest Elements
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Cesium has the largest atomic radius
going from 273.1pm to 260pm and
Rubidium comes next with an atomic
radius around 30. But is still always
positive.
Question 1
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What is the largest atomic radius going
from 273. 1pm to 260pm.
Answer: Cesium
Question 2
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The number of valence electrons stays
the same in atomic radius.
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Answer: T
T or F
Question 3
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Atomic Radius is used in pictometers?
T or F
Answer: T
Question 4
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As the trend goes across the electrons?
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A. Increase
B. Decreases
C. Stays the same
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Answer: A
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Question 5
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What are the smallest element in
atomic radius?
A. Lithium and neon
B. Hydrogen and copper
C. Hydrogen and Neon
D. None of the above
Answer: C
Question 6
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What are the largest elements in atomic
radius?
A-Radon and Lithium
B-Cesium and Rubidium
C-Francium and Uranium
D-none of the Above
Answer: B
Ionic Radius
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When atoms lose electrons and become
cations, the atoms become smaller.
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They lose valence electrons
The nucleus pulls the rest in tighter.
When atoms gain electrons and become
anions, they atoms become larger.
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They gain valence electrons
The nucleus can’t pull them in as tightly.
Trends
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Across a period- On the left the cations
are smaller. On the right the anions are
larger, but overall…Atomic radius
decreases.
Down a group-Atomic radius increases
Review
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True or False. The cations from group
1 to group 2 decreases.
True
Review
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True or False. The anions on the right
side of the periodic table decreases
across the period.
True