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Chemical Periodicity
Atomic Structure and
Atomic Size– Quantum mechanical model doesn’t
sharply define boundary to limit size– Atomic radius: ½ the distance between
nuclei of 2 like atoms in a diatomic molecule
Atomic radius
• •
Atomic size
Atomic SizeA
tom
ic S
ize I
ncr
easi
ng
Atomic Size Increasing“Fatty Francium”
Octet Rule: atoms want 8 e- in their valence energy level
Ionization Energies: amount of energy required to remove an electron from the valence shell of an atom
Nobel Gases - don’t want to lose e- so they have very high
ionization energyLi - doesn’t take much energy to lose e-, low ionization energyF - wants to gain an e- , therefore takes large amount of energy to pull off an e-, high ionization energy
• Which atom has the larger radius?
–Be or Ba
–Ca or Br
Ba
Ca
Examples
▫As you move down a group the ionization energy decreases b/c of the shielding effect
e- e-
+
e- e-
e-
e- e-
e-
e- e-
e-
Inner e- tend to push outer e- away from the nucleus b/c both have
negative charges
▫As a result of this shielding effect outer e- are less tightly bound to the nucleus than inner e-
Ionization Energy Increase
Ion
izatio
n E
nerg
y Incre
ase
D. Ionization Energy (cont.)
• Ion – positively (cation) or negatively (anion) charged atom, gains or loses electrons
Ionic Size
Cations Increase
Ion
ic S
ize I
ncr
ease
Anions Increase
• Which atom has the higher ionization energy
–N or Bi
–Ba or Ne
N
Examples
Ne
Electronegativity• The electronegativity of an element is the
tendency for the atoms to attract e- when they are chemically combined with another element
• Noble Gases have NO electronegativity b/c they don’t gain e-
• Increase from left to right b/c of octet rule• Decrease when move down a group b/c of
shielding effect
Electronegativity Increase
Ele
ctron
eg
ativity In
crease
E. Electronegativity (cont.)
Periodic Table of the
Elements
Atomic Size Increasing
Ato
mic
Siz
e I
ncr
easi
ng
Ionic Size Increasing
Ion
ic S
ize I
ncr
easi
ng
“Fatty Francium”
Fr
F. Summary of Trends
Ionization Energy Increase
Ion
izatio
n E
nerg
y Incre
ase
Electronegativity Increase
Ele
ctron
eg
ativity In
crease
F
“FriendlyFluorine”
Whiteboard PracticeWhich of these elements has a larger atomic size?
Arrange these elements in order of increasing atomic size.
S, Cl, Al, NaAnswer: Cl, S, Al, NaAnswer: Cl, S, Al, Na
Is this a period trend or a group trend?
Answer: Period trendAnswer: Period trend
1. Li or K2. C or O 4. Ca or K
3. Te or I
White Board PracticeWrite the element with the greatest value for
Ionization Energy.
Rank the sets of atoms from smallest to largest for Electronegativity.
1. Al or P
2. Ca or Ni
3. O or Ne
4. Zr or Cs
1. Se, Cr, Zn Cr, Zn, Se
2. P, Ar, Mg Ar, Mg, P
Atomic Size War!Atomic Size War!• Each card has an element symbol. • You will flip over one card and place it on the table and your
partner will do the same.• Who ever has the Element with the GREATER atomic size Wins
those two elements.• You continue to each flip over cards until one player has all the
elements.• If you flip over the same element you will each turn over one
more card and the player with the greater atomic size will win all four cards.
• Separate the cards and shuffle and play a new game using a different trend.