(A): Differentiate between Isotopes and Isobars …

• The  unstable  isotopes  which  emit  various  types  of  radiations  are  known  as  radioactive isotopes.

• The atoms of different elements having different atomic numbers but the same mass number are known as isobars.

• Bohr's Model of an Atom:

Niels Bohr, revised Rutherford’s atomic model and put forth the following suggestions:

Neils  Bohr  proposed  that  the  electrons  possess  a  specific  amount  of  energy which allows  them  to revolve around the nucleus. The electrons are confined to these energy levels.  While  revolving  in  these  discrete  orbits,  the electrons  do  not  radiate  energy.  Hence, these orbits  are  also  known  as stationary  orbits or stationary shells. Smaller the size of the orbit, smaller is its energy.

As we move away from nucleus, the energy of the orbit increases progressively. The  transfer  of  an  electron  from  one  orbit  to  another  is  always  accompanied  with  absorption  or emission of energy. When an electron jumps from a lower energy level to a higher energy level, it absorbs energy. When an electron returns from a higher energy level to a lower energy level, it emits energy.