CHAPTER 3: THE
A. MENDELEEV'S PERIODIC
LAW
PERIODIC TABLE
• Mendeleev's periodic law states that the "physical and
chemical properties of the elements are periodic function
of their atomic masses
B. MODERN PERIODIC LAW
C.
·
"
Modern periodic law states that the physical &
chemical properties of the elements are periodic functions
of their atomic numbers.
"
PERIODICITY IN PROPERTIES: Repetition of similar
properties after regular intervals is called periodicity in
properties.
, CAUSE :
•
•
When elements are arranged in the increasing order
of their atomic numbers, elements with similar
properties are repeated at regular intervals.
These
regular intervals are
2,8,8, 18, 18 or 32 when elements
with similar electronic configuration of the valence shell
are repeated. These numbers are called magic
numbers.
D. MENDELEEV'S ORIGINAL PERIODIC TABLE
called periods.
1. This table is divided into 8 vertical columns called groups
7 horizontal rows 2. Elements
were arranged according to
&
, according to similar properties & atomic
masses (in increasing
order)
3. This table did not contain the
zero group
Since inert
gases
were not known at that time.
4. DEFECTS:
(a) POSITIONS Of ISOTOPES: Atoms of same
element having different
atomic mass are called
isotopes. They
were not given separate
positions
(b) No PLACE LEFT VACANT FOR NOBLE GASES
(C) Elements with higher atomic mass have been
placed before the
elements of lower atomic
mass.
-
, Example - Ar (at. mass = 40) & K (at mass =
39)
Co (at. mass =
58.94) &
Ni (at. mass =
58.69)
intervals and
have same number of valence
elections & distribution in the valence shell.
E. MENDELEEV'S MODIFIED PERIODIC TABLE
1. In Mendeleev's modified periodic table, clements have been
arranged in
the increasing order of their atomic
numbers.
2. Elements with similar properties are repeated after
certain
they
ледивая
A. MENDELEEV'S PERIODIC
LAW
PERIODIC TABLE
• Mendeleev's periodic law states that the "physical and
chemical properties of the elements are periodic function
of their atomic masses
B. MODERN PERIODIC LAW
C.
·
"
Modern periodic law states that the physical &
chemical properties of the elements are periodic functions
of their atomic numbers.
"
PERIODICITY IN PROPERTIES: Repetition of similar
properties after regular intervals is called periodicity in
properties.
, CAUSE :
•
•
When elements are arranged in the increasing order
of their atomic numbers, elements with similar
properties are repeated at regular intervals.
These
regular intervals are
2,8,8, 18, 18 or 32 when elements
with similar electronic configuration of the valence shell
are repeated. These numbers are called magic
numbers.
D. MENDELEEV'S ORIGINAL PERIODIC TABLE
called periods.
1. This table is divided into 8 vertical columns called groups
7 horizontal rows 2. Elements
were arranged according to
&
, according to similar properties & atomic
masses (in increasing
order)
3. This table did not contain the
zero group
Since inert
gases
were not known at that time.
4. DEFECTS:
(a) POSITIONS Of ISOTOPES: Atoms of same
element having different
atomic mass are called
isotopes. They
were not given separate
positions
(b) No PLACE LEFT VACANT FOR NOBLE GASES
(C) Elements with higher atomic mass have been
placed before the
elements of lower atomic
mass.
-
, Example - Ar (at. mass = 40) & K (at mass =
39)
Co (at. mass =
58.94) &
Ni (at. mass =
58.69)
intervals and
have same number of valence
elections & distribution in the valence shell.
E. MENDELEEV'S MODIFIED PERIODIC TABLE
1. In Mendeleev's modified periodic table, clements have been
arranged in
the increasing order of their atomic
numbers.
2. Elements with similar properties are repeated after
certain
they
ледивая
