Transcript Unit #4: Periodic Table

Unit #4: Periodic Table
Chapter 5
The Periodic Table

Origin of the Table
1. J.W. Dobereiner (early 1800’s) German
a. observed that several elements
could be organized into groups of
three- called “triads”
b. elements of each triad shared similar
properties
2. J.A.R Newlands (1865)- English
a. arranged table according to atomic
mass
b. observed periodicity of the elements
c. law of octaves: properties of
elements repeat every eighth
element
3. Dmitri Mendeleev (1869)- Russian
a. Published first table that is the basis for today’s
periodic table
b. arranged elements by increasing atomic mass
c. assigned elements with similar properties to the same
columns
d. predicted existence of missing elements based on his
table
e. problem: some elements did not fit according to their
atomic mass and properties
- I / Te
- Co / Ni
- Ar / K
4. H.G.J. Moseley (1913)- English
a. developed idea of atomic number
b. used x-rays to determine the atomic number
of elements
c. corrected Mendeleev’s table by arranging
elements according to atomic number, not
atomic mass
d. founded modern periodic law: when
elements are arranged in order of
increasing atomic number, their physical
and chemical properties show a periodic
pattern
B. Reading the Table
1. Be familiar with the location of:
a. Alkali metals
b. Alkaline earth metals
c. Metalloids
d. Transition metals
e. Nitrogen family
f. Oxygen family
g. Halogens
h. Noble gases
i. s, p, d, f blocks
j. Horizontal rows- period or series
k. Veritcal columns- group or family
l. Most probable charge and outer shell
configuration
C. Periodic Trends
1. Atomic Radius
a. the distance from the center of
an atom’s nucleus to its outer
most electron
decrease
increase
Decrease – Left  Right
Increase – Top  Bottom
2. Ionic Radius
a. no clear trend
b. take in electron
- ionic radius increases
- + charged nucleus is attracting
more electrons
- full outer shell results in increased
repulsion among electrons
c. remove electron
- ionic radius decreases
- + charged nucleus is attracting
fewer electrons
3. Ionization Energy
a. Energy required to move an electron
increase
increase
Increase – Left  Right
Top  Bottom
4. Electronegativity
a. an atom’s ability to attract electrons
in a chemical bond
increase
increase
Increase – Left  Right
Top  Bottom