What is isotope in simple words?


In simple words, an isotope is a variation of the same element with a different number of neutrons in its nucleus.

What is isotope in simple words


Isotopes are variations of chemical elements that have a variable number of neutrons but the same number of protons and electrons. As a result of a difference in the total number of neutrons in their respective nuclei, isotopes are variations of elements with different nucleon numbers (total number of protons and neutrons).

Hydrogen Isotopes

isotopes of hydrogen

The periodic table’s first element, hydrogen, has an atomic number of one. Isotopes are defined as elements with the same atomic number but a different mass number. Protium 1H1, deuterium 1H2 or D, and tritium 1H3 or T are the three hydrogen isotopes. All three of them have different mass numbers because the isotopes have varying amounts of neutrons


It is one of the most prevalent hydrogen isotopes. The natural abundance of protium is 99.98%. Protium has a mass of 1.007825 amu.


Its nucleus contains a proton and a neutron. The deuteron is the name for the hydrogen-2 nucleus. It doesn’t emit radiation. Its compounds are utilized as solvents for hydrogen 1 and in chemical analysis. Heavy water is enhanced with deuterium. It functions as a neutron moderator and coolant. Nuclear fusion also uses hydrogen 2 as a fuel.


Its nucleus has one proton and two neutrons. The interaction of cosmic rays with atmospheric gases results in minute amounts of tritium, often known as hydrogen 3, appearing in nature. Additionally, they are briefly released when nuclear bombs are tested. The atomic mass of hydrogen 3 is 3.0160492 u.

Carbon Isotopes

isotopes of carbon

Carbon is at the top of the fourth group in the periodic table having atomic number 6 and mass number 12.

Carbon has 3 isotopes


The isotope of carbon that is the most abundant is Carbon-12. It contains six protons and six neutrons. Its natural abundance is 98.8%.


The second isotope of carbon is called Carbon-13 having 7 neutrons in addition to six protons with a natural abundance of 1.1%.


The third isotope namely Carbon-14 has 8 neutrons plus 6 protons in its nucleus and has a natural abundance of 0.009%.

Oxygen Isotopes

  • Oxygen-16
  • Oxygen-17
  • Oxygen-18
isotopes of oxygen

Three stable isotopes of the element oxygen (O), 16O, 17O, and 18O, exist in nature. Each of these oxygen isotopes has a nucleus made up of eight protons and either eight, nine, or ten neutrons.

Chlorine Isotopes

Chlorine is the second member of the halogen family and has atomic number 17 and mass number 35.5.

Chlorine has 2 isotopes


The first isotope having the greater natural abundance is chlorine-35.It contains 17 protons and 18 neutrons and a percentage abundance of 75.7%


The second isotope of chlorine is chlorine-37 containing 17 protons and 20 neutrons and a percentage abundance of 24.3%.

Why isotopes are unstable?

Why isotopes are unstable?

How are isotopes formed?

Isotopes can be created artificially by bombarding a stable nucleus with charged particles using accelerators or neutrons in a nuclear reactor, or they can be created naturally through the radioactive decay of a nucleus (i.e., emission of energy in the form of alpha particles, beta particles, neutrons, and photons).

Uses of Isotopes

  • Radioactive iodine is used in diagnosing thyroid problems
  • Cobalt-60 is used in killing cancer cells and also for the shrinkage of tumours
  • Some radio-isotopes are used for determining molecular structures.
  • They are also used to study different reaction mechanisms.
  • Carbon-14 is used to trace the path of carbon in photosynthesis


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