Chapter 5: Periodic Law
History of Periodic Table (Book section 5-1)
1. Dalton: Periodic Table based on Atomic mass #, A
2. Johann Dobereiner (1780-1849):
Triads: Cl, Br, and I had similar properties
3. Cannizaro: standardized method of determining A#
(1860)
4. Newlands: Law of Octaves (periodic repeats of properties
elements) (1864)
of
5. Mendeleev: organized PT into rows & columns; he predicted as
yet undiscovered elements and their prop. ( ex: Ga, Sc, Ge). He stated
the original Periodic law
6. Meyer: developed the same PT as Mendeleev but he
predictions
7. Ramsey: Noble gases 1890’s
8. Moseley: P.T. bases on Z; not masses. (Modern P.T.)
(1914) Worked with Rutherford
He developed and stated the modern Periodic Law.
Exceptions to original P. Table
Co & Ni
Te & I
K & Ar
Z = 27 and 28
Z =19 and 18
A = 58.9 and 58.6
Z =39.1 and 39.9
p. 1
made
no
Modern P.T.
*Based on Z number (# of protons) (Book section 5-2)
Periodic Law: Physical & chemical properties of elts are a periodic (cyclic)
function of their atomic numbers Z
1. Based on e- configurations
2. Periods across the PT n= 1-7
3. Representative Group or Family
IA
IIA
IIIA
IVA
VA
VIIA
VIIA
VIIIA
IA-VIIA
Alkali M
Alkaline Earth M
Aluminum Family
Carbon Family
Nitrogen Family
Oxygen Family (chalcogen)
Halogen
Noble Gases
ns1
ns2
ns2np1
ns2np2
ns2np3
ns2np4
ns2np5
ns2np6
4. Transition M (B Elements)
Fill d orbitals:
Metals have a charge of +1 or +2 since T. metals have 1 or 2 valence
electrons (s) and all have similar properties
Ex:___________________ _______________
5. Inner Transition Elements (1900’s)
4f & 5f
all have similar prop.
4f Lanthanides:
Rare earth
5f Actinides:
All radioactive
Th, Pa, U, Np found in nature others made in lab
Homework; Periodic table with colors and labels
p. 2
Representative Elts
Metals (M)
Metalloids
Non-Metals (NM)
Both Properties of
M and NM
Na, K, Cu
Si, Ge
Cl, N, O
Lustrous
Malleable
Non-lustrous - Dull
Zigzag line
Good insulators
SemiConductors
Ductile
Brittle
Good conductors
Poor conductors
Heat/ electricity
Heat/ electricity
Solid at RT except____
Example:
Coal Gases
3 or fewer outer e-
5 or more outer e-
Tend to lose outer e-
Tend to gain e-
Form + Ions
Form - Ions
Octet Rule:
 Atoms will gain, lose or share electrons in order to become stable
 Atoms will gain , lose or share to obtain an electron configuration like the
noble gas
 Ions – electrically charged particles; formed by gaining (anions) or losing
(cations) electrons
 Homework: plot the graphs
 p. 3
Periodic Trends (pp. 140-154) Book section 5-3)
1. Study Figure 5-14.
 Describe what happens to atomic radius as one moves down a group.
 Describe what happens to atomic radius as one moves across a period.
 Practice Problems (p.142)

o Sample Problem 5-5 Mg versus Cl
o
o largest ____________ smallest __________
o
o Sample Problem 5-5 Na versus P
o
o largest ____________ smallest __________
2. Study Figure 5-16
 Which element has the highest I.E.? Mg or Cl


 Which element has the highest I.E.? Na or P


 What happens to the radius of an atom when it loses electrons to form a
positive ion?


 What happens to the radius of an atom when it gains electrons to form
a negative ion?

p.4
3. Define Ionization energy.
4. Define electronegativity
5. Define Electron Affinity
6. Define Ionic Radius
p.5
Review
I. History: development of the Period Table
Metal vs. Non-Metals
1817 Dobereiner
1863 Newlands
1869 Mendeleev
1890 Ramsey
1913 Moseley
 Periodic Law
II. Modern Table: based on electron configurations groups,
periods (sublevel blocks)
III. Periodicity of Elements (to be studied)
a. Electron configuration patterns
b. Atomic radius - size
c. Ionization energy – energy required to remove an
electron
d. Electron affinity – energy gained or released when an
electron is gained
e. Ion formation
f. Electronegativity – a scale developed by Linus Pauling
to use to determine types of chemical bonds
p. 6