The document discusses the history and development of the periodic table. It explains that Mendeleev was the first to publish a periodic table in 1869, organizing elements based on atomic mass and recognizing that elements with similar properties fell into vertical columns. However, Mendeleev's table had some anomalies, like incorrect placement of some elements. Moseley later proposed using atomic number instead of atomic mass, solving these anomalies. The modern periodic table is organized into periods and groups based on atomic number, with blocks for different orbital types. It provides information about elemental properties and reactions.

1. By: Farhan Hameed

2. The periodic table organizes the elements in a
particular way. A great deal of information about
an element can be gathered from its position in
the period table.

3.  For example, we can predict with reasonably good
accuracy the physical and chemical properties of
the element. We can also predict what other
elements a particular element will react with
chemically.

4.  Understanding the organization and plan of the
periodic table will help us to obtain basic
information about each of the 118 known
elements.

5.  In 1869, a Russian chemist called
Mendeleev published a periodic table ,
he realized that the physical and
chemical properties of elements
were related to their atomic mass
in a 'periodic' way, so that groups of
elements with similar properties fell
into vertical columns in his table.

6.  Position of Hydrogen
 The position of hydrogen was not correctly defined. It
was placed in Group I although its properties
resembled both the Group I elements (the alkali
metals) and the group VII elements (the halogens).

7.  Grouping of Some Elements
 In some cases Mendeleev placed elements according
to their similarities in properties and not in increasing
order of their atomic masses, while some dissimilar
elements were grouped together. Thus, the position
of these elements was not justified. For example,
cobalt (at. mass 58.9) was placed before nickel (at.
mass 58.6); copper and mercury are similar in their
properties but were placed separately. Copper was
placed in group I although it did not resemble the
elements of this group.

8.  Anomalous Pair
 In certain pairs of elements like, Ar (40) and K (39); Co
(58.9) and Ni (58.6); Te (127.6) and I (126.9) the
arrangement was not justified. For example, argon was
placed before potassium whereas its atomic mass is
more than potassium.

9.  Isotopes
 Isotopes are atoms of the same element having
different atomic mass but same atomic number. For
e.g., there are three isotopes of hydrogen with
atomic mass 1, 2, and 3. According to Mendeleev's
periodic table these should be placed at three
separate places. However isotopes have not been
given separate places in the periodic table.

10.  Moseley's Periodic Table
Using atomic number instead
of atomic mass as the organizing
principle was first proposed by the
British chemist Henry Moseley
in 1913, and it solved anomalies
that seem in Mendeleev’s periodic
table.

11.  Modern Periodic law states as,
“The properties of elements are the periodic function of
their atomic number not atomic masses”

13. Groups
Verticals columns in periodic table , it is 18 in
number.

14. Periods
Horizontal rows in periodic table, it is 7 in number.

15. Groups
Sub Group A
(Representative
Elements)
S-Block
P-Block
Sub Group B
(Transition
Elements)
D-Block
F-Block

17. S-Block
(groups)
I-A
(Alkali family)
II-A
(Alkaline earth
metals)

18. P-Block
(groups)
III-A
(Boron family)
IV-A
(Carbon family)
V-A
(Nitrogen
family)
VI-A
(Oxygen family)
VII-A
(Halogens)
VIII- A
(Noble gases)

19.  D-block called Outer Transition Elements.
F-Block
Lanthanide
series
Actinide
series
(14 Elements)

20.  Elements which have small no. of e- in there valence
shall.
 All s , d and f block elements and few of p-block are
metals.

21.  Elements which have large no. of e- in there valence
shall.
 Most p-block elements are non metals.

22.  Metals and non-metals are separated by a heavy steep
diagonal line, which physical appearance like metals
some non-metallic properties as well.