1. Atomic Size (radius) Ionization Energy Electronegativity
Periodic Trends
Atomic Size (radius)
Ionization Energy
Electronegativity
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2. What’s the key idea? Remember: It’s all about the pull!
How much attraction is there between the protons and the electrons?
How much “inward pull” do the protons have on the electrons in the outer shell?
Remember, those electrons are called _________________________ electrons.
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3. Trends in Atomic Size
One way to think about atomic size is to look at the units that form when atoms of the same element are joined to one another.
These units are called molecules.
Because the atoms in each molecule shown below are identical, the distance between the _________ of these atoms can be used to estimate the size of the atoms.
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4. This size is expressed as an atomic radius.
Trends in Atomic Size
This size is expressed as an atomic radius.
The atomic radius is ______________ of the distance between the nuclei of two atoms of the same element when the atoms are joined.
Often measured in picometers (pm)
One trillion picometers = one meter
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5. ______________ from top to bottom within a group
Trends in Atomic Size
In general, atomic size…
______________ from top to bottom within a group
______________ from left to right across a period
Remember, protons pull electrons toward the center of the atom.
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6. Why does atomic size _____________ down a group?
Trends in Atomic Size
Why does atomic size _____________ down a group?
More protons (more “nuclear charge”) means _______________ inward pull on the electrons
HOWEVER…
There are more occupied energy levels (more “shells” of electrons)
So the valence electrons are “___________” by the inner electrons and aren’t pulled in as much
The “shielding effect” is _______________ than the increase in nuclear charge
So atomic size ___________________
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7. Why does atomic size _____________ across a period?
Trends in Atomic Size
Why does atomic size _____________ across a period?
More protons (more “nuclear charge”) means _____ inward pull on the electrons
Electrons are also being added, but they are being added to the _________ energy level so there is no additional “shielding”
So atomic size ________________
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8. Trends in Atomic Size
The figure below summarizes the group and period trends in atomic size.
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9. Trends in Ionization Energy
Electrons can move to higher energy levels when atoms __________ energy. Sometimes the electron has enough energy to overcome the attraction of the _________ in the nucleus.
The energy required to remove an electron from an atom is called ionization energy.
The energy required to remove the first electron from an atom is called the first ionization energy.
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10. Trends in Ionization Energy
In general, ionization energy…
______________ from top to bottom within a group
______________ from left to right across a period
Remember, protons pull electrons toward the center of the atom.
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11. Trends in Ionization Energy
Why does ionization energy _________ down a group?
As you move down the group, _________ are being added to the next energy level
These outer electrons are more “______________” by the inner electrons
They have _____________ attraction to the protons in the nucleus
___________________ to remove
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12. Trends in Ionization Energy
Why does ionization energy _________ across a period?
More ________________ are being added
Greater ________________ charge
Protons have _____ inward pull on electrons
___________________ to remove
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13. Trends in Ionization Energy
The figure below summarizes the group and period trends for the first ionization energy.
Energy generally increases
Energy generally decreases
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14. Trends in Electronegativity
There is a property that can be used to predict the type of bond that will form during a reaction.
This property is called electronegativity.
Electronegativity is the ability of an atom of an element to attract ___________________ when the atom is in a compound.
Usually expressed in “Pauling units”
We don’t have electronegativity values for the noble gases because they have a full valence shell (they are “happy”)  they don’t form many compounds
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15. Trends in Electronegativity
In general, electronegativity…
______________ from top to bottom within a group
______________ from left to right across a period
Remember, protons pull electrons toward the center of the atom.
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16. Trends in Electronegativity
Why does electronegativity _________ down a group?
As you move down the group, electrons are being added to the _____ energy level
The protons in the nucleus are “____________” by multiple energy levels
__________ pull
Less ability to attract additional _________
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17. Trends in Electronegativity
Why does electronegativity _________ across a period?
More ______________ are being added
Greater _______________ charge
More ___________
____________ ability to attract electrons
Draw the NaCl example below:
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18. This figure summarizes several trends that exist among the elements.
OVERALL
This figure summarizes several trends that exist among the elements.
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