Respuesta :

b.125                                                                                                                                   no of electrons=atomic no                                                                                          no of neutrons+no of electrons=mass no                                                                     no of neutrons=mass no-no of electrons                                                                        no of neutrons=210-85                                                                                                     no of neutrons=  125                                                                        

 

  • There are 125 neutrons contained in the atom

  • Atomic number can be regarded as the number of electrons in that atom.
  • Hence, atomic number = 85, and number of electrons is 85

  • Mass number is the addition of number of electrons as well as number of neutrons. It can be calculated as
  • Mass number = ( number of electrons) + ( number of Neutron)

  • ( number of Neutron) = (Mass number ) -  ( number of electrons)

Substitute the values

  • ( number of Neutron) = ( 210 - 85)

= 125

Therefore, the correct option is B, which is  125 electrons

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