2. HISTORY OF PERIODIC TABLE OF ELEMENTS
The First Attempt:
-The periodic table of elements was first attempted to be made by a French
geologist, A.E.Beguyer de Chancourtois.
He positioned elements according to increasing atomic weight.
-The “Father” of the Periodic Table:
-Chemists Lothar Meyer and Dmitri Mendeleev were both working during the
same time period to create the periodic table of elements. They were both
producing similar results, but they were working completely independent of
each other.
-Unfortunately for Meyer, Mendeleev’s periodic
table was available for the community before
Meyer’s.
Dmitri Mendeleev
3. -Mendeleev's periodic table of 1869 contained 17 columns
with two partial periods of seven elements each.
- In 1871 Mendeleev revised the 17-group table with eight
columns.
-The table contained gaps because Mendeleev predicted the
discovery of new elements.
-Unlike the modern periodic table, Mendeleev’s was arranged
in order by increasing atomic mass. Today the elements are
correctly arranged by increasing atomic number.
4. This is Mendeleev’s Periodic table after he revised it in 1871, adding the
8th
group.
5. This is the modern Periodic Table of Elements
used today all around the world.
6. -Henry Moseley later found that the properties of elements depend
on the structure of their atoms and vary with atomic numbers in a
systematic way. This was used to make the modern periodic table of
elements.
-The atomic number is the same as the number of protons in an
atom’s nucleus.
-In the periodic table of elements, the elements are put into periods
and groups.
7. Period:
Periods are the horizontal rows in the periodic table.
The number of the period is the same as the number of
electrons in the outermost electron orbital of an element in
that period.
Group:
Groups are the vertical columns in the periodic table.
Elements in the same group have similar properties.
8. -There are three types of elements in the periodic table of elements.
The three types are Metals, Non-Metals, and Metalloids.
Physical Properties of Metals:
-Luster (shininess)
-Good conductors of heat and electricity
-High density (heavy for their size)
-High melting point
-Ductile (most metals can be drawn out into thin wires)
-Malleable (most metals can be hammered into thin
sheets)
Chemical Properties of Metals:
-Easily lose electrons
-Corrode easily.
9. Nonmetals
Nonmetals are found to the right of the stair step line. Their
characteristics are opposite those of metals.
Physical Properties of Nonmetals:
-No luster (dull appearance)
-Poor conductor of heat and electricity
-Brittle (breaks easily)
-Not ductile
-Not malleable
-Low density
-Low melting point
Chemical Properties of Nonmetals:
-Tend to gain electrons
Since metals tend to lose electrons and nonmetals tend to gain
electrons, metals and nonmetals like to form compounds with each
other.
These compounds are called ionic compounds. When two
or more nonmetals bond with each other, they form a covalent
compound.
10. Since metals tend to lose electrons and
nonmetals tend to gain electrons, metals and nonmetals
like to form compounds with each other. These compounds
are called ionic compounds. When two or more nonmetals
bond with each other, they form a covalent compound.
-The group of gases on the right edge of the table are
known as noble Gases or inert gases.
Noble gases
-Chemically nonreactive (This is because they
have a complete valence shell.)
-Little tendency to gain or lose electrons.
-Low boiling points (all are gases at room
temperature)
11. Metalloids
Elements on both sides of the zigzag line have properties of both
metals and nonmetals. These elements are called metalloids.
Physical Properties of Metalloids:
-Solids
-Can be shiny or dull
-Ductile
-Malleable
-Conduct heat and electricity better than nonmetals but
not as well as metals
