Define the first and second ionization energy. State why the second ionization energy of elements is higher than first ionization energy?

• The first ionization energy is the energy it takes to remove an electron from a neutral atom.  
• The second ionization energy is the energy it takes to remove an electron from a 1+ ion.   
• After the removal of first electron, force of attraction between the nucleus and remaining outer most electrons increase. So, to remove 2nd electrons more amount of energy is required. Hence, the second ionization energy is higher than first ionization energy.