ATOMIC NUMBER AND MASS NUMBER

ATOMIC NUMBER AND MASS NUMBER

  • Atomic number of an element  Total number of protons present in the nucleus Total number of electrons present in the neutral atom
  • Atomic number is represented by Z.
  • Mass number of an element  No. of protons  No. of neutrons
  • Mass number is represented by A.

 

Isotopes, Isobars, and Isotones

Isotopes 

  • Atoms of the same element having same atomic number but different mass number are called isotopes.
  • Isotopes are atoms of same element.
  • They have same number of protons but different number of neutrons.
  • They have same number of electrons.
  • They occupy same position in the periodic table.
  • They have similar chemical properties.

Applications of isotopes :

  • An isotope of uraniumis used as a fuel in nuclear reactors. 
  • An isotope of cobaltis used in the treatment of cancer. 
  • An isotope of iodineis used in the treatment of goitre. 

Example : 11H , 12H , 13H

 

Isobars

  • Atoms of different elements with different atomic number but same mass number are called isobars.
  • Isobars are atoms of different elements.
  • They have different number of protons and neutron.
  • They have different number of electrons.
  • They occupy different positions in the modern periodic table.
  • They have different chemical properties.

Example :

1840Ar , 2040Ca

Isotones

Atoms of different elements having the same number of neutrons are called isotones. 

Example : 614C , 7N15