Chapter 5
The Periodic Table
History of the Periodic Table
*By 1860 more than 60 elements were known
Stanislao Cannizzaro (1826-1910)
- Found a method to determine atomic
mass
Dimitri Mendeleev (1834-1907)
– “Father of the Periodic Table”
-Made the first accepted Periodic Table
-Noticed trends and left empty spaces for
“missing” elements
History of the Periodic Table
Henry Moseley (1887 – 1915)
– Found a method to determine
atomic number (# of protons)
Periodic Law
Properties of elements are based on atomic
number and valence electrons
Modern Periodic Table
-Arranged by atomic numbers so elements
with similar properties fall in the same
columns
-Newest sections added: Lanthanides,
Actinides, Noble Gases
Electron Configurations Revisited
Valence Electrons:
-Outer Shell Electrons
-Have the Highest Principle Quantum
Number
-Determine many properties of the atoms
Example:
Arsenic:
Electron Configurations Revisited
Periodic Table Arrangement:
Period
# of Elements
Energy Sublevels
Maximum
# of
Electrons
2
2
2
8
8
3
8
4
5
18
18
8
18
6
32
32
7 If finished… 32
32
1
18
s orbital
p orbital
d orbital
f orbital
Period Prediction
Using only the ELECTRON CONFIGURATION…
Example:
1s22s22p63s23p64s23d104p3
Located in PERIOD 4
(the highest principle
quantum number)
Group Prediction
Using only the Electron Configuration…
Example:
1s22s22p63s23p64s23d104p3
Located in Group 15 - Add
the ELECTRONS from the
highest PERIOD (includes s,
d if any, and p if any)
Blocks on the Periodic Table
s block:
-Group 1 = Alkali Metals
-Soft
-Extremely reactive
(but…Hydrogen is NOT a metal)
-1 valence electron
Blocks on the Periodic Table
s block:
-Group 2 = Alkali-Earth Metals
-2 valence electrons
-Reactive,
but less than Group 1
(Go down to “Video clip” half way down page)
Blocks on the Periodic Table
p block:
-Groups 13-18
-Properties vary
greatly
(due to “steps”)
-Valence Electrons
= Group # - 10
example:
Blocks on the Periodic Table
p block:
-Group 17 = Halogens
– Very reactive
A halogen lamp also uses a tungsten filament, but it is
encased inside a much smaller quartz envelope.
Because the envelope is so close to the filament, it would
melt if it were made from glass. The gas inside the
envelope is also different -- it consists of a gas from the
halogen group. These gases have a very interesting
property: They combine with tungsten vapor. If the
temperature is high enough, the halogen gas will combine
with tungsten atoms as they evaporate and redeposit
them on the filament. This recycling process lets the
filament last a lot longer. In addition, it is now possible to
run the filament hotter, meaning you get more light per
unit of energy. You still get a lot of heat, though; and
because the quartz envelope is so close to the filament, it
is extremely hot compared to a normal light bulb.
(http://home.howstuffworks.com/question151.htm)
Blocks on the Periodic Table
p block:
-Group 18 = Noble Gases
– Very unreactive
- They have a stable (full) valence octet
-Many used in creating signs
Neon signs are luminous-tube signs that
contain neon or other inert gases at a low
pressure. Applying a high voltage (usually a
few thousand volts) makes the gas glow
brightly. They are produced by the craft of
bending glass tubing into shapes. A worker
skilled in this craft is known as a glass bender,
neon or tube bender.
(http://en.wikipedia.org/wiki/Neon_sign)
Blocks on the Periodic Table
d block:
-Groups 3-12
-Called the TRANSITION METALS
-Luster, conductive, Malleable, Ductile
examples:
-Hg is the ONLY liquid metal
Keep Your Paws Off Mercury video
Blocks on the Periodic Table
f block:
Lanthanides
Actinides
(Layout can vary slightly)
Periodic Properties (aka TRENDS)
1. Strength of the Nucleus
STRONGER
Periodic Properties (aka TRENDS)
1. Strength of the Nucleus
W
E
A
K
E
R
Periodic Properties (aka TRENDS)
2. Atomic Radius (size of an atom)
SMALLER
Periodic Properties (aka TRENDS)
2. Atomic Radius
L
A
R
G
E
R
2. Atomic Radius
Periodic Properties (aka TRENDS)
ION = Atom with a charge due to gain or loss of
(an) electron(s)
3. Ionization Energy (Energy to REMOVE an electron)
Increases
Periodic Properties (aka TRENDS)
Decreases
3. Ionization Energy
Periodic Properties (aka TRENDS)
4.
Electron Affinity (Energy change when an
electron is ADDED)
-When EASY to add an electron – EA is EXOTHERMIC /
NEGATIVE
-When DIFFICULT to add an electron – EA is
ENDOTHERMIC / POSITIVE
Periodic Properties (aka TRENDS)
4. Electron Affinity
Easier / More Exothermic
Periodic Properties (aka TRENDS)
4. Electron Affinity
More Difficult / More Endothermic
Periodic Properties (aka TRENDS)
5.
Ionic Radius (Size of ion)
Cation = LOST electron(s)
Has POSITIVE charge
SMALLER than the neutral atom – due to less
electrons, so nucleus can pull better on each eLost 1
electron
Now ALL of these electrons
get pulled in a little bit!
Potassium Atom =
19 protons and 19 electrons
Potassium ION =
19 protons and 18 electrons
Periodic Properties (aka TRENDS)
5.
Ionic Radius (Size of ion)
Anion = Gained electron(s)
Has NEGATIVE charge
Larger than the neutral atom – due to more
electrons, so nucleus can’t pull as well on each e-
The extra e-.
Now all of the
electrons move
out a little bit.
Periodic Properties (aka TRENDS)
6.
Electronegativity - Ability to attract electrons
Higher
Periodic Properties (aka TRENDS)
6.
Electronegativity
Decreases
Graphing of Trends
Example Questions
1. Which is smaller – C or O?
2. Which is larger – Be or Be+2 (Be ion)?
3. Which has a more exothermic electron
affinity – Na or P?
4. Which has a more endothermic electron
affinity – K or Cs?
5. Which has a higher ionization energy –
Ga or Se?
6. Which has a higher electronegativity – F
or Br?