Question

In the periodic table, the maximum chemical reactivity is at the extreme left (alkali metals) and extreme right (halogens). Which properties of these two groups are responsible for this?

• A. Least ionisation enthalpy on the left and highest negative electron gain enthalpy on the right.
• B. Non-metallic character on the left and metallic character on the right.
• C. Small atomic radii on the left and high atomic radii on the right.
• D. Highest electronegativity on the left and least electronegativity on the right.

Answer 1

The correct option is A Least ionisation enthalpy on the left and highest negative electron gain enthalpy on the right.

High chemical reactivity of alkali metals is due to low ionisation energies. Alkali metals readily lose an electron and form cation with stable noble gas electronic configuration. High chemical reactivity of halogens is due to high negative electron gain enthalpies. Halogens readily accept an electron and form anion with stable noble gas electronic configuration.