Ispopes, Isotones and Isobars

Forum Expert
Posted on
11 Aug 2010 12:50:20 IST
Posts: 7804
11 Aug 2010 12:50:20 IST
0 people liked this
0
3639 View Post
Ispopes, Isotones and Isobars
Engineering Entrance , JEE Main , JEE Main & Advanced , Chemistry , Physical Chemistry

 It is interesting to note that atoms of a given atomic number can have different number of neutrons. Some examples are listed below:

Hydrogen

Hydrogen atom (Z = 1) has no neutrons.Number of protons = 1Number of electrons = 1Number of neutrons = 0It has been reported that the hydrogen element has atoms with mass number 2 and 3 also i.e.,Atoms of elements having the same atomic number with different mass numbers are called isotopes.

isotopes of hydrogen
protium deuterium tritium are the types of isotopes

Nuclear composition of isotopes of chlorine:

Nuclear composition of isotopes of chlorine
isotope of chlorine

 

Nuclear composition of isotopes of carbon:
Nuclear composition of isotopes of carbon

 

isotope of carbon

 

Characteristics of Isotopes

  • All isotopes of an element have the same number of valence electrons thus have identical chemical properties.
  •   The physical properties of the isotopes are different due to the difference in the number of neutrons in their nuclei. The densities, melting points and boiling points etc., are slightly different.

Reason for Fractional Atomic Masses of Elements

Atomic masses of many elements are in fractions not in whole numbers.

Example:

Cl - 35.5Cu - 63.5The fractional atomic masses of elements are due to the existence of isotopes having different masses.

Example:1

Natural chlorine consists of two isotopes:Calculate the average atomic mass of chlorine.

Example: 2

A naturally occurring sample of Lithium contains 7.42% of 6Li and 92.58% of 7Li. The relative mass of6Li is 6.015 and that of 7Li is 7.016. Calculate the atomic mass of a naturally occurring sample of lithium.

Solution:

Example: 3

Which of the following two nuclei are isotopes of each other?

Solution:

The two isotopes are:

Radioactivity

Isobars

The atoms of different elements, which have the same mass number but different atomic numbers are called isobars. These have different number of protons but equal sum of number of protons and neutrons.

Some Typical Isobars

Isobars Atomic number(Z) MassNumber(A) Electrons(e) Proton(p) Neutron(n)
 
40  Ar18  
 18  40  18  18  22(40-18)
 
40   K 19
 19  40  19  19  21(40-19)
 
40    Ca 20
 20  40  20  20  20(40-20)

Isotones

The atoms of different elements, which have the same number of neutrons but different atomic numbers, are called isotones.

Some Typical Isotones

 

Isotones Atomic number(Z) MassNumber(A) Electrons(e) Proton(p) Neutron(n)
 
14  C  6  
 6  14 6  6 8(14-6)
 
15   N 7
 7  15  7  7  8(15-7)
 
16    O 8
8 16  8 8  8(16-8)

 

Before we end let us appreciate how far the theory of the atoms and their structure has progressed since Dalton made first proclamations on the existence of the atom. Here is a comparison of Dalton's atomic theory with the Modern theory of atoms.

Comparison of Dalton's Atomic Theory and Modern Atomic Theory

 

 Dalton's Atomic Theory  Modern Atomic Theory
 All matter is made up of extremely small particles called atoms  An element is made up of extremely small particles called atoms
 Atoms are indivisible and indestructible  Atoms are divisible and are no more indestructible
 Atom is the smallest particle of an element  Atom consists of still smaller subatomic particles like proton, electron and neutron
 All atoms of an element are alike in all respects  All atoms of an element may not be alike; they can have different masses (e.g. isotopes)
 Atoms take part in all chemical reactions; the relative number and kinds of atoms are constant in a given compound  Atoms take part in all chemical reactions; the relative numbers and kinds of atoms are constant in a given compound

 


 


Quick Reply


Reply

Some HTML allowed.
Keep your comments above the belt or risk having them deleted.
Signup for a avatar to have your pictures show up by your comment
If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team
Free Sign Up!
Sponsored Ads

Preparing for JEE?

Kickstart your preparation with new improved study material - Books & Online Test Series for JEE 2014/ 2015


@ INR 5,443/-

For Quick Info

Name

Mobile

E-mail

City

Class

Vertical Limit

Top Contributors
All Time This Month Last Week
1. Bipin Dubey
Altitude - 16545 m
Post - 7958
2. Himanshu
Altitude - 10925 m
Post - 3836
3. Hari Shankar
Altitude - 10085 m
Post - 2217
4. edison
Altitude - 10825 m
Post - 7804
5. Sagar Saxena
Altitude - 8635 m
Post - 8064
6. Yagyadutt Mishr..
Altitude - 6330 m
Post - 1958