Difference between Isotopes, Isobars and Isotones
In this lesson ,
the Difference between Isotopes, Isobar and Isotones will be discussed with
some Common Examples for all types.
What are Isotopes?
Isotopes may be
defined as:
(1) The atoms of an element which have the same
number of protons and different number of neutrons are called Isotopes.
(2) The atoms of an element which have the
same atomic number but different atomic masses or mass numbers.
** Since
isotopes of an element have the same atomic number, each of these contains
equal number of protons.
** They have
different atomic masses which is accounted for by the different number of
neutrons present in the nucleus.
** Thus the
isotopes of an element are characterised by different number of neutrons in the
nucleus.
Examples of Isotopes
** Isotopes of
Hydrogen: There are three
isotopes of hydrogen : protium 1H1, deuterium 2H1 or
D , and tritium 3H1 or T .
** Isotopes of
Neon: Neon has been found to consist of three
isotopes : 20Ne10, 21Ne10, 22Ne10
** Isotopes of
Oxygen: Oxygen has three
isotopes : 16O8 , 17O8 , 18O8
** Isotopes of
Chlorine: Chlorine is a mixture of two isotopes : 35Cl17 ,35Cl17
** Isotopes of
Uranium: There are three isotopes of uranium : 234U92 , 235U92
, 238U92 ,
What are Isobars?
** Isobars are
The atoms which have the same mass number but different atomic numbers are
called isobars.
** The word isobar meaning ‘equally heavy’ is taken from the Greek isos = equal, and barys = heavy.
** The word isobar meaning ‘equally heavy’ is taken from the Greek isos = equal, and barys = heavy.
Examples of isobars
** For
example, 40 Ar18 , 40K19 , 40Ca20 are
isobaric atoms. Similarly, 235U92, 235Np93, 235Pu94 are
isobars.
** Since isobars have the same mass number, the
number of protons plus neutrons in the nucleus in each of these is equal.
** The number of
protons being given by atomic number (Z), the number of neutrons is, therefore,
(A – Z) where A is the mass number.
** The number of
extranuclear electrons is equal to (Z).
What are Isotones?
** Isotones are
: Atoms which have different atomic number and different atomic masses but the
same number of neutrons .
** Isotones are
different elements having entirely different atomic structure. They have
different physical and chemical properties.
Examples of isotones:
(1) 14C6 , 15N7 , 16O8 are
isotones since each contains eight neutrons
(2) 30Si14 , 31P15 , 32S16 are
isotones. Each contains sixteen neutrons.
(3) Some other
examples of isotones are :
Reference: Essentials of Physical Chemistry /Arun
Bahl, B.S Bahl and G.D. Tuli / multicolour edition.
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