Sun and Nuclear Energy

 Q The mass number of isotope of an element is 239. If its nucleus has 145 neutrons, what is its atomic number?

  • Mass no = no of protons + neutrons
  • no of protons = 239-145 =94
  • No of protons = atomic no = 94
Q The number of protons in the nucleus of an element of mass number 239 is 90 what will be the number of neutrons in its isotope of mass no 243?
  • First isotope contains 90 protons, the second isotope will also contain 90 protons.
  • Number of neutrons is equal to mass number - number of protons
  • 243-90 =153
Q The atomic number of an element having mass number 230 is 90. What will be the number of protons and neutrons in its nuclei?
  • Atomic number is equal to number protons equal to 90.
  • Number of neutrons is equals to mass number - number of protons.
  • 230 - 90 = 140
Q The mass number of an element is 18. If it contains seven electrons, what will be the number of protons and neutrons in it? What is the atomic number of the element?
  • Number of electrons is equal to number of protons is equal to seven.
  • Mass number equal to number of protons plus neutrons
    • 18 = 7+ no of neutrons 
    • Neutrons = 18-7 =11
  • Atomic number of an element equal to number of protons equal to seven.
Q Give me the number of protons, neutrons, and electrons per atom in the two isotopes of chlorine 35 cl 17 and 37 cl 17?
  • 35 cl 17
    • Number of protons equal to 17
    • Number of neutrons equal to 35-17, equal to 18.
    • Number of electrons equal to 17.
  • 37 cl 17
    • Number of protons equal to 17. 
    • Number of neutrons equal to 37-17 = 20.
    • Number of electrons equal to 17.

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