Based on the above data, answer the following questions: i. Identify the element having highest atomic number.
The first ionization enthalpies of 5 elements of second period are given below:
| Element | 1st IE values (kJ mol-1) |
| I | 520 |
| II | 1681 |
| III | 1086 |
| IV | 2080 |
| V | 899 |
Based on the above data, answer the following questions:
i. Identify the element having highest atomic number.
ii. If element I is lithium, how will you explain its low value of first ionization enthalpy?
iii. Explain why ionization enthalpies are always positive.
1 Answers
i. Element IV. The first ionization enthalpy increases with increase in atomic number along a period. Hence, the element IV having highest IE will have highest atomic number among the given elements.
ii. Alkali metals have only one electron in their valence shell which can be easily lost resulting in the stable noble gas configuration. Therefore, lithium shows low value of first ionization enthalpy.
iii. Energy is always required to remove electrons from an atom. Hence, ionization enthalpies have positive value.