Periodic TrendsLearning Target:• 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

Periodic TrendsA. 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.

Periodic TrendsCoulomb’s Law

Periodic Trends2. Effective nuclear charge (Zeff)- the net nuclear pull experienced by the valence electrons in an atom.

a. Zeff = # protons - # core (non-valence) electrons

Periodic Trends

http://inntrending.com/effective-nuclear-charge-trends/

Periodic Trends

http://inntrending.com/effective-nuclear-charge-trends/

Periodic Trends3. 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.

Periodic Trends

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

Periodic Trends

Periodic Trends• B. Periodic trends are patterns

in the periodic table relating to the size and other properties of elements.

Periodic Trends1.ATOMIC RADIUS is the

distance between the nucleus and the outer edge of the electron cloud.

Periodic Trends

Periodic Trends

Periodic Trends

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

Periodic Trendsa) 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.

Periodic Trends

Periodic Trends

Periodic Trendsb. EXCEPTIONS!!!

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

Periodic Trendsb. 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.

Periodic Trends3. ELECTRONEGATIVITY is the ability of

an atom in a molecule [meaning it’s participating in a bond] to attract shared electrons to itself.a. Think of the atoms as playing “tug

of war” with their outer shell electrons.

Periodic Trends

Periodic Trends

Periodic Trends4.IONIC RADIUS is the distance

from the nucleus to the outer edge of the electron cloud in a charged ion.

Periodic Trendsa. Cation- the atom LOST electron(s),

has a positive chargeb. Anion- the atom GAINED

electron(s), has a negative chargec. All atoms want a full valence shell,

and will gain/lose electrons to get there.

Periodic TrendsCharges of Ions

Periodic Trends

Periodic TrendsC. Periodic trends can be justified by using one of the following generalizations:

1. Use Z eff to explain trends across a period.2. Use electron shielding (increased energy

levels, increased distance) to explain trends down a group.