Isotopes

• Isotopes

  • Although the number of protons in a particular element is always the same, the number of neutrons can be different
  • Isotopes are atoms of the same element that have an equal number of protons but a different number of neutrons
  • In the diagram below are three isotopes of Hydrogen:
• Hydrogen has three isotopes, each with a different number of neutrons

  
• • Isotopes occur naturally, but some are more rare than others
  • For example, about 2 in every 10,000 Hydrogen atoms is Deuterium
  • Tritium is even more rare (about 1 in every billion billion hydrogen atoms)
  • The number of neutrons in an atom does not affect the chemical properties of an atom, such as its charge, but only its mass
  • This is because neutrons have no charge but do have mass
  • In the periodic table, the mass number of Chlorine is often given as 35.5
• This section of a periodic table shows Chlorine as having a mass number of 35.5, but other elements have an integer mass number

  
• • The mass number of chlorine is given as 35.5 because it has 2 isotopes, one with a mass number of 35 and the other with a mass number of 37
  • Chlorine-35 is about three times more abundant than chlorine-37, so the given mass number of chlorine is closer to 35 than 37
  • The number of electrons and protons in different isotopes remains the same
  • Some isotopes are unstable as they have an imbalance of protons and neutrons