Calcium has 2 Valence electrons which are easy to remove. From the ionization energy values, I1 = 589.5 kJ/mol, I2 =1145 kJ/mol, I3= 4900 kJ/mol, I4 = 6500 kJ/mol, and I5 = 8100 kJ/mol, the energy difference between the 2nd and 3rd electron is the highest because the energy required to remove the 3rd electron is geeatest which implies that the 3rd electron must be a completed octet-orbital electron which is more difficult to remove than other electrons
For any element to exhibit the pattern of ionization energy shown in the question, it must possess five electrons in its outermost shell. These five electrons are not lost at once. They are lost progressively until the valence shell becomes empty. The ionization energy increases steadily as more electrons are lost from the valence shell.
The only pentavalent element among the options in arsenic, hence the answer.
In this case, when performing units conversions involving two proportional factors we need to make sure we first convert to the base unit and then to the target one; thus, since 1 kg = 1000 g and 1 g = 1000 mg, we set up the following expression:
