Organizing the Elements
The Periodic Table
water, wind, and fire.
Correspond with solid,
liquid, gas, and
A few elements have been known for thousands
of years: copper, silver, and gold.
Only 13 elements were discovered by the year
When chemists started using the scientific
method, the rate increased to finding 5 new
elements in 10 years.
Chemists needed a way to organize the
elements- used the properties of the elements to
sort them into groups.
J.W. Dobereiner (1780-1849)
Published a classification
system where elements
were put into triads.
A triad is a group of 3
elements with similar
An example of on such
triad is chlorine, bromine,
Chlorine, Bromine, and Iodine
Chlorine, Bromine and Iodine
Look different or have different physical
Have similar chemical properties.
-all react easily with metals.
The average atomic masses of chlorine
and iodine is 81.177 amu. This is close to
bromine which is in the middle of the
Russian chemist in
1869 who published a
chart of elements
elements in order of
Mendeleev’s Periodic Table
question marks where
he predicted elements
He predicted their
properties as well as
their position on the
1913, determined an
atomic number for
Helped arrange the
periodic table in order
of increasing atomic
When elements are arranged in order of
increasing atomic number, there is a periodic
repetition of their physical and chemical
What are the 4 classical elements? (early
Who was the first to try and arrange a
How did Mendeleev’s periodic table differ
from the modern periodic table?
What did Henry Moseley contribute to the