1. Periodic Trends Learning Target: Criteria For Success:
I can use the Periodic Table to identify and explain periodic trends, including atomic and ionic radii, electronegativity, and ionization energy.
Criteria For Success:
I can explain effective nuclear charge and electron shielding.
I can explain how increasing effective nuclear charge across a period influences the atomic radius, electronegativity and ionization energy.
I can explain how increased electron shielding down a group influences atomic radius, electronegativity and ionization energy.
I can explain the trend of ionic radius and how the magnitude and the sign of the ionic charge influences ionic radius

2. Periodic Trends A. Attraction between the nucleus and electrons
1. Coulomb’s law- the force of attraction between two oppositely charged particles is directly proportional to the magnitude of the charges and inversely proportional to the distance between those charges.

3. Periodic Trends
Coulomb’s Law
𝐹= 𝑘 𝑞 1 𝑞 2 𝑟 2

4. Periodic Trends 2. Effective nuclear charge (Zeff)-
the net nuclear pull experienced by the valence electrons in an atom.
a. Zeff = # protons - # core (non-valence) electrons

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3. Electron shielding- the inner electrons shield the outer electrons from some of the nucleus’ attractive force.
a. Going down a group adds another principle energy level  adds more shielding.

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b. Adding another energy level also increases the distance between the outer electrons and the nucleus which decreases the force- Coulomb’s Law!

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B. Periodic trends are patterns in the periodic table relating to the size and other properties of elements.

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ATOMIC RADIUS is the distance between the nucleus and the outer edge of the electron cloud.

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IONIZATION ENERGY is the energy required to remove an electron from the atom.

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Each additional electron requires MORE energy to remove than the previous one, so the second ionization energy will be greater than the first ionization energy, and so on.

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19. Periodic Trends EXCEPTIONS!!!
O vs. N- It’s easier to remove an electron from O because of the repulsion of the paired electrons.

20. Periodic Trends EXCEPTIONS!!!
Be vs. B- It’s easier to remove an electron from B because it’s a p electron vs. an s electron and electrons in p orbitals are held less tightly.

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ELECTRONEGATIVITY is the ability of an atom in a molecule [meaning it’s participating in a bond] to attract shared electrons to itself.
Think of the atoms as playing “tug of war” with their outer shell electrons.

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IONIC RADIUS is the distance from the nucleus to the outer edge of the electron cloud in a charged ion.

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Cation- the atom LOST electron(s), has a positive charge
Anion- the atom GAINED electron(s), has a negative charge
All atoms want a full valence shell, and will gain/lose electrons to get there.

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Charges of Ions

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C. Periodic trends can be justified by using one of the following generalizations:
1. Use Z­eff to explain trends across a period.
2. Use electron shielding (increased energy levels, increased distance) to explain trends down a group.