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ALevel

Chemistry-9701

Isotopes

Paper 1 & 2

Isotopes
 

1: What Is An Isotope?

> Isotopes are atoms that contain the same number of protons, but they have different number of neutrons.

> This also could be understood as isotopes are those atoms which have the same proton number (atomic number) but a different nucleon (mass) number.

> Note: all atoms that are of the same element contain the same number of Protons.

> Nucleon or mass Number: number of protons and neutrons in an atom.

> Proton or atomic Number: number of protons in an atom.


2: Notation In Isotopes:

                                      
        Cambridge International Examinations Syllabus 2022-2024

> In an isotope which is shown by A (above) the “x” represents the Nucleon or Mass number (the number of protons and neutrons) while the “y” represents the Proton or Atomic number (the protons in an atom). 
 
          
           Cambridge International Examinations Lawrie Ryan, Roger Norris

Note: an isotope of Lithium above will have the same number of protons (Proton or atomic number) but different number of neutrons (Nucleon or Mass number)

>An illustration of what was earlier mentioned is shown with:


 
               Cambridge International Examinations Lawrie Ryan, Roger Norris

The above diagram shows the atomic structure and isotopic symbols of the three isotopes of hydrogen

> In the above diagram each isotope of the hydrogen atom has different numbers of neutrons. However, the number of neutrons remains the same. In effect, the proton or atomic number does not change but the nucleon or mass number changes on each one of the isotopes that are present.

3: Why The Isotope Of The Same Element Has The Same Chemical Properties?


> Isotopes belonging to the same element have been known to show the same chemical properties because they have the same number of electrons present in the atom. This would also mean they have the same electronic structure.


4: Why Isotope Of The Same Element Has Different Physical Properties? (Limited To Mass And Density)


> Mass is the amount of matter present in something and density is mass per unit volume. With that idea in mind, things that have different masses will have different weights.

> Different isotopes of the same element have a different number of neutrons resulting in having a different mass number or nucleon number hence they do not all weigh the same or have the same mass or density.

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