Question

Any body help me? please Q 17

Answer 1

Question 17

 The subscript  2  is the  atomic number   for helium  and subscript  4  is the mass   number for Helium

 explanation

  when  writing   down  an isotope  of   an  element the mass  number of that isotope  is written  in upper   side  of the chemical  symbol,  while atomic  number  is written  on the  lower  side.

Since 4  is on upper side it is the mass  number of He, while 2  is  the atomic  number since  it is  on lower side.

Question 18

The type of radiation  emitted  when polonium -212  form lead 208  is  an alpha  particle

explanation

Alpha  decay  is a decay in which  an  atomic  nuclei  emit an alpha  particles and be transformed  into different atomic  nuclei  with    a mass  number that is  reduced by 4

polonium  212  is reduced by 4  to  form lead 208  therefore it undergo  alpha  particle  decay.