Question

In which reaction is the first ionization energy greatest?1.na + energy → na+ + e−2.k + energy → k+ + e−3.mg + energy → mg+ + e−4.al + energy → al+ + e−?

Answer 1

The answer would be the 3. Mg + energy--> mg+ + e- 
Ionization Energy is the amount of energy vital to eliminate the most loosely bond electron from an atom in the gas stage. Since Magnesium has a higher first energy which is 738 kj/mol, is the energy needed to remove the outermost, or highest energy.

Answer 2

Answer: Option (d) is the correct answer.

Explanation:

The energy required to remove the most loosely bound electron from a neutral gaseous atom is known as ionization energy.

As the atomic size of an atom increases then there will be less force of attraction between the nucleus and valence electrons of the atom. Hence, with lesser amount of energy the valence electrons can be removed.

As a result, ionization energy will decrease.

Now, potassium is larger in size than sodium. Hence, ionization energy of potassium is less than sodium.

And, Na, Mg and Al are all period 3 elements. It is known that across a period there is an increase in ionization energy of the elements due to decrease in their atomic size.

Hence, aluminium being the smallest will have the greatest ionization energy.

Thus, we can conclude that the reaction $Al + energy \rightarrow Al^{+} + e^{-}$ will have the greatest first ionization energy.