Transcript Mole Quantity Conversions

Periodic Trends
Periodic Trends
• describe characteristics of elements across
periods and among families
• are not absolute – represent general trends
• are based largely on the “shielding effect”
Shielding Effect
• The protection provided by the inner core electrons
which lessens the nucleus’s pull on the outer valence
electrons
• Across a period, it does not play a significant role (all
elements in a period have valence electrons in the same
outermost energy level).
• Down a family, it plays an increasingly more
significant role (each family member has an additional
layer of core electrons, moving the valence electrons
further away from the nucleus).
Atomic Radius
Definition: half the distance between the nuclei of
like atoms in a solid
Trend: decreases from left to right and increases from
top to bottom
Electronegativity
Definition: measure of attraction an atom has for a
unshared pair of electrons
Trend: increases from left to right and decreases from top
to bottom (excluding noble gases)
Ionization Energy
Definition: amount of energy needed to release an
electron from a gaseous atom
Trend: increases from left to right and decreases from top
to bottom
Reactivity
Metals: are more reactive with small ionization
energies, small electronegativity values, and
large atomic radii
-Trend: down and to the left
Francium: most reactive metal
Nonmetals: are more reactive with large ionization
energies, large electronegativity values, and small
atomic radii
-Trend: up and to the right (excluding noble gases)
Fluorine: most reactive nonmetal
Reactivity
Periodic Trends Examples
Which of the following is the largest atom:
Li, Rb, or Fr? Fr
Periodic Trends Examples
Rank the following atoms by decreasing
atomic radius: Cs, Pb, At. Cs  Pb  At
Periodic Trends Examples
Which of the following has the greatest
ionization energy: Rb, Sr, I, or O? O
Periodic Trends Examples
Rank the following in order of increasing
ionization energy: Cs, Bi, Rn, F.
Cs  Bi  Rn  F
Periodic Trends Examples
Which of the following has the greatest
electronegativity: Li, Cs, or K? Li
Periodic Trends Examples
Rank the following in order of decreasing
electronegativity: Fr, As, F. F  As  Fr
Periodic Trends Examples
Which metal is more reactive, Cs or Ca?
Cs
Periodic Trends Examples
Which nonmetal is more reactive, C or N?
N