Because atoms with similar electron configurations react similarly, we can see trends or patterns in the periodic table.
There is no sharp boundary to an atom, but we can get a rough measure of atomic size from the most probable electron distance from the nucleus, the area that contains 90% of the electron density. This distance is called the atomic radius.
Atomic Radius is effected by “Effective Nuclear Charge” – the charge of the nucleus felt by an electron. As ENC increases, the atomic radius decreases. I.E. a strong positive nucleus will pull in more negative electrons. Atomic radius Decreases as you move across a period and increases as you move down a group
Both electron affinity and ionization energy deal with isolated atoms, where as Electronegativity allows us to compare an elements attractive force to electrons when their atoms are combined.
Periodic table intro2
Organize the following classes into categories.
Chemistry 101 Marketing 214 Art 323
Music 211 Physics 404 Speech 105
Calligraphy 324 Biology 324 Phys Ed 010
Astronomy 212 Economics 103 Sculpture 102
Writing 462 Finance 321 Poetry 209
English 104 Phys. Ed 005 Business 412
Where did the Periodic Table
– J.W. Dobereiner
• Triad Classification
– John Newlands
• Law of Octaves
– Dmitri Mendeleev
• Credited with modern
Still Not Perfect
Atomic Mass: 39.10 amu
• Highly reactive Metal
Atomic Mass: 39.95 amu
• Inert gas
*Important fact you may want to right down*
The Modern Periodic Table is based on atomic
number and electron configuration, not atomic mass.
• When elements are
arranged in order of
number, there is a
of their physical and
Ya’ll best line up d’em elements in
order of increasing proton number
to pick out the properties!
• Have only a few
electrons in outer
most energy level.
• Lose e-
positive ions (X+
• Good Conductors
• Malleable (sheets)
• Ductile (wire)
• Often Lusterous
• More than 3 e-
• Gain electrons to form
negative ions (X-
• Dull in appearance
• Have properties of metals & nonmetals
• Positioned on metal / nonmetal line
• B, Si, Ge, As, Sb, Te, Po, At
A Groups = Main Group Elements
IA IIA VIAVIIA VIIIA
IB – VIIIB
INNER TRANSITION METALS
(Lanthanide & Actinide Series)
3B 4B 5B 6B 7B 8B 1B 2B
Pick a Trend, Any Trend
1. Atomic Size
2. Ionization Energy
3. Electron Affinity
No definite shape, but scientist can get a rough
It doesn’t depend on Weight Watchers
The energy required to remove
an electron from an atom in
the gas phase.
A(g)+ Energy A+
(g) + e-
Ionization energy measures
how tightly an electron is
held in the atom.
Ionization Energy (cont.)
• More and more energy is required to move
each electron from an atom
• Metals generally have low IE.
• Nonmetals have high IE.
• IE increases as you move across a period
and decreases as you go down a group or
EA – It’s NOT a clothing company
• The energy used or released for a
gaseous atom to gain an electron.
A(g) + e-
(g) + Energy
Electron Affinity (cont.)
In general. . .
• EA increases (becomes more negative) as you go across a
period and decreases as you go down a group or family.
• The greater the electron affinity, the greater the IE.
– Metals have lower EAs
– Nonmetals have higher EAs
A comparative scale relating the abilities of
elements to attract electrons when their
atoms are combined.
• Active metals (IA) have the lowest Ens
• Most nonmetals have the highest Ens