Question
Explain isotopes, isobars, isotones and isomers by giving examples.
✓
Answer
→ (i) Isotopes :
→The atoms which have atomic number Z same but atomic mass number A different, then such type of atoms are called the isotopes of each other.
→For example :
Isotopes of hydrogen are ${ }_1 H ^1,{ }_1 H ^2,{ }_1 H ^3$
•${ }_1 H ^1$ - there is one proton but having no neutron.
• ${ }_1 H ^2$ - there is one proton one neutron.
• ${ }_1 H ^3$ - there is one proton and two neutrons.
→Isotopes of carbon are ${ }_6 C ^{12},{ }_6 C ^{13},{ }_6 C ^{14}$
→Isotopes of uranium are ${ }_{92} U ^{233},{ }_{92} C ^{235},{ }_{92} C ^{238}$
→ (ii) Isobar :
→Atoms having same atomic mass number A , but different atomic number Z are called the isobars of each other.
→ For example :
${ }_1 H ^3$ and ${ }_2 He ^3$
${ }_{82} Pb^{214}$ and ${ }_{83} Bi ^{214}$
→ (iii) Isotone :
The atoms for which the neutron number N is the same but atomic number Z and mass number A are different are called isotones to each other.
→ For example :
${ }_{80} Hg ^{198} \text { and }{ }_{79} Au ^{197}$
→ (iv) Isomer :
→The atoms for which the atomic number Z and mass number A are same but their radioactive properties are different are called isomers of each other.
→For example :
${ }_{35} Br ^{80}$ contains a pair of isomers.
→The atoms which have atomic number Z same but atomic mass number A different, then such type of atoms are called the isotopes of each other.
→For example :
Isotopes of hydrogen are ${ }_1 H ^1,{ }_1 H ^2,{ }_1 H ^3$
•${ }_1 H ^1$ - there is one proton but having no neutron.
• ${ }_1 H ^2$ - there is one proton one neutron.
• ${ }_1 H ^3$ - there is one proton and two neutrons.
→Isotopes of carbon are ${ }_6 C ^{12},{ }_6 C ^{13},{ }_6 C ^{14}$
→Isotopes of uranium are ${ }_{92} U ^{233},{ }_{92} C ^{235},{ }_{92} C ^{238}$
→ (ii) Isobar :
→Atoms having same atomic mass number A , but different atomic number Z are called the isobars of each other.
→ For example :
${ }_1 H ^3$ and ${ }_2 He ^3$
${ }_{82} Pb^{214}$ and ${ }_{83} Bi ^{214}$
→ (iii) Isotone :
The atoms for which the neutron number N is the same but atomic number Z and mass number A are different are called isotones to each other.
→ For example :
${ }_{80} Hg ^{198} \text { and }{ }_{79} Au ^{197}$
→ (iv) Isomer :
→The atoms for which the atomic number Z and mass number A are same but their radioactive properties are different are called isomers of each other.
→For example :
${ }_{35} Br ^{80}$ contains a pair of isomers.
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