How many elements have more ionisation energy as compared to their next higher atomic number element?
Na, Mg, Al, Si, P, S, Cl, Ar
Correct answer is '3'. Can you explain this answer?

Question

How many elements have more ionisation energy as compared to their next higher atomic number element?Na, Mg, Al, Si, P, S, Cl, ArCorrect answer is '3'. Can you explain this answer?

Answer

Explanation:

Ionisation energy is the energy required to remove an electron from a gaseous atom or ion. It increases as we move from left to right across a period of the periodic table, i.e., as the atomic number increases. Therefore, the ionisation energy of an element is generally higher than its next higher atomic number element. However, there are some exceptions to this trend, which can be explained by the electronic configuration of the elements.

Analysis of each element:

Na: Sodium has one electron in its outermost shell, which is easier to remove than the electrons in the inner shells. Therefore, its ionisation energy is lower than its next higher atomic number element (Mg).

Mg: Magnesium has two electrons in its outermost shell, which are more difficult to remove than the single electron in the outer shell of sodium. Therefore, its ionisation energy is higher than its next higher atomic number element (Al).

Al: Aluminum has three electrons in its outermost shell, which are easier to remove than the electrons in the inner shells. Therefore, its ionisation energy is lower than its next higher atomic number element (Si).

Si: Silicon has four electrons in its outermost shell, which are more difficult to remove than the three electrons in the outer shell of aluminum. Therefore, its ionisation energy is higher than its next higher atomic number element (P).

P: Phosphorus has five electrons in its outermost shell, which are easier to remove than the electrons in the inner shells. Therefore, its ionisation energy is lower than its next higher atomic number element (S).

S: Sulfur has six electrons in its outermost shell, which are more difficult to remove than the five electrons in the outer shell of phosphorus. Therefore, its ionisation energy is higher than its next higher atomic number element (Cl).

Cl: Chlorine has seven electrons in its outermost shell, which are easier to remove than the electrons in the inner shells. Therefore, its ionisation energy is lower than its next higher atomic number element (Ar).

Ar: Argon has eight electrons in its outermost shell, which are more difficult to remove than the seven electrons in the outer shell of chlorine. Therefore, its ionisation energy is higher than its next higher atomic number element (none).

Conclusion:

Out of the given elements, there are only three elements (Mg, Si, and Ar) that have more ionisation energy as compared to their next higher atomic number element. The electronic configuration of these elements explains their higher ionisation energy as compared to their next higher atomic number element.

Answer

2.0 Order of ionization energy
Na < M g > Al < Si < P > S < Cl < Ar

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