MCQ Detailed View

Atoms are characterized by three main numbers: the atomic number (Z), the mass number (A), and the number of neutrons (N). The atomic number (Z) is the number of protons in the nucleus, which determines the identity of the element. The mass number (A) is the sum of protons and neutrons. The number of neutrons is obtained by subtracting Z from A (N = A – Z).

When different elements have the same number of neutrons but different numbers of protons, they are called isotones. For example, carbon-14 (₆C¹⁴) and nitrogen-15 (₇N¹⁵) both contain 8 neutrons. Although they belong to different elements (carbon and nitrogen), they are isotones because their neutron number is the same.

It is important to distinguish isotones from other related terms:

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  Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons. Example: hydrogen-1, hydrogen-2 (deuterium), and hydrogen-3 (tritium).

  
  


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  Isobars: Atoms of different elements with the same mass number but different atomic numbers. Example: argon-40 (₁₈Ar⁴⁰) and calcium-40 (₂₀Ca⁴⁰).

  
  


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  Isotones: Atoms of different elements with the same number of neutrons.

  
  

The concept of isotones is especially useful in nuclear chemistry and nuclear physics because neutrons strongly influence the stability of the nucleus. Elements with the same number of neutrons often show similar nuclear properties, even though their chemical properties differ because the proton number changes.

Thus, elements that have the same number of neutrons are specifically referred to as isotones.