Trends in the Periodic Chart
…position  electronsphysical
and chemical properties…
• …the position indicates physical and
chemical properties of elements!
There are two effects:
• Attraction—
• Shielding—
There are two effects:
• Attraction— as Z increases, attraction increases
BUT
• Shielding— as Z increases, shielding increases:
--a little bit with each electron in the same period
--in a great jump as you start the next period
Shielding
• Shielding is the weakening of attraction
due to electrons interfering with the
attraction of the nucleus
• Shielding increases a little as you go
across a period (not as much as attraction)
• Shielding jumps tremendously as you start
a new energy level
Periodic trends
Simple
Valence electrons
– The representative (tall) columns represent
the number of valence electrons
– Transition elements have only two valence
electrons, but have a part-filled d sublevel
How many valence electrons?
Simple
Electron configurations
EC ends in…
EC ends in…
ns1
ns2
*
*
*
EC ends in…
*
*2
ns
(n-1)d?
ns2(n-2)f14(n-1)d?
ns2(n-2)f?
*
EC ends in…
*
ns2np?
*
*
ns2(n-1)d10np?
ns2 (n-2)f14 (n-1)d10np?
Simple
Ionization pattern
• Metals have
-only a few valence electrons
-lose these electrons to empty their
valence level
-form positive ions
Simple
Ionization pattern
• Non-metals have
-more valence electrons
-gain electrons to fill valence level
-form negative ions
What is the charge on the ion?
Medium
Atomic size
• In a column, a lower row indicates an extra
energy level
• Outer energy levels are larger (due to
shielding)
• The largest atom in a column is the bottom
element
Medium
Ionization energy
Medium
• Ionization energy— the energy required
to remove an electron
X + IE X+ + e• Outer energy levels are farther from the
nucleus
• It is easier to remove an electron from a
larger energy level
• The lowest ionization energy is at the
bottom of the column
Medium
Electronegativity
—the attraction an atom has for a
shared pair of electrons
• See previous—the highest
electronegativity is at the top
Medium
Electron affinity
—the attraction an atom has for an
electron from outside
X + e- X- + EA
• See previous—the highest electron affinity
is at the top
One moment…
As you go across a row, you get
more protons in the nucleus
• They attract the electrons better
• Each energy level gets smaller
Hard
•
•
•
•
Atoms get smaller as you go across a row
Ionization energy gets larger
Electronegativity gets larger
Electron affinity gets larger
--All because there are more protons—
Z increases faster than shielding in a
period
Recap
• Atomic size
• INCREASES as you go down
and left
Recap
• Electronegativity, ionization energy, and
electron affinity
• INCREASE as you go up
and right
Pop Quiz
• Which element on the entire periodic chart
is the largest?
• Smallest?
• Which element on the entire periodic chart
has the largest IE?
• Smallest?
Pop Quiz
• Which element on the entire periodic chart
has the largest e-negativity?
• Smallest?
• Which element on the entire periodic chart
has the largest EA?
• Smallest?
Pop Quiz
• Who’s your favorite pop star?
• Which has the greatest / least: Size, IE,
EA, e-neg?
C
F
Sn
I
The diagonal effect
• Of the previous four elements, the ones in
the same row and column are easy, right?
• What can you say about carbon and
iodine?
• Try this– they might be just about the
same!
The metal/nonmetal line
Diagonal effect!
(probably electron affinity)
Hard (cont’d)
Ionic radius
Negative ions are (way) larger than their
atom
Positive ions are (way) smaller than their
atom
• Which has the largest / smallest ion?
Li
Be
K
Ca
• Which has the smallest / largest ion?
Mg
S
Sr
Te
• Which has the smallest / largest ion?
+2
Mg
+2
Sr
S
Te
-2
-2
Hard (cont’d)
Second and third ionizations
• If you ionize an atom, you make a (+) ion
• It’s harder to ionize it again
• It gets way harder after you empty the
valence level
Hard (cont’d)
Second and third ionizations
• If you ionize an atom, you make a (+) ion
• It’s harder to ionize it again
• It gets way harder after you empty the
valence level
Why?
Hard (cont’d)
• First, second, and third ionization energies
X + IEX+1 + eX+1 + IE2X+2 + eX+2 + IE3X+3 + e-
Disclaimers
• Noble gasses have no electronegativity—
they don’t share electrons
• Noble gasses have no electron affinity—
they don’t gain electrons
• Most metals have no electron affinity—
they don’t gain electrons
Ionization Energies in kJ/mol
• 1
2
3
H 1312
He 2372
5250
Li 520
7297
11810
Be 899
1757
14845
B 800
2426
3659
C 1086
2352
4619
N 1402
2855
4576
O 1314
3388
5296
F 1680
3375
6045
Ne 2080
3963
6130
Na 496
4563
6913
Mg 737
1450
7731
4
5
21000
25020
6221
7473
7467
8408
9361
9541
10545
32820
37820
9442
10987
11020
12180
13350
13627
Ionization Energies in kJ/mol
• 1
2
3
H 1312
He 2372
5250
Li 520
7297
11810
Be 899
1757
14845
B 800
2426
3659
C 1086
2352
4619
N 1402
2855
4576
O 1314
3388
5296
F 1680
3375
6045
Ne 2080
3963
6130
Na 496
4563
6913
Mg 737
1450
7731
4
5
21000
25020
6221
7473
7467
8408
9361
9541
10545
32820
37820
9442
10987
11020
12180
13350
13627
Electron Affinity*, Electronegativity*,
Ionization energy
Size
Atomic number, shielding, diagonal
effect
Reactivity
Melting point?
State!
Know these oxides
Know these oxides
Acidic
Basic
Amphoteric