Question

Atomic number of element with lowest first ionisation enthalpy is

• A. 32
• B. 19
• C. 35
• D. 87

Hint:

To find the element with the lowest ionization energy, focus on the alkali metals, especially those with the lowest atomic numbers (e.g., Francium).

Answer 1

The Correct Option is D

The first ionization enthalpy refers to the energy required to remove one mole of electrons from one mole of atoms in their gaseous state.
- Elements with low ionization enthalpy are typically found in Group 1 of the periodic table. These elements have a single electron in their outermost shell, making it easier to lose this electron.
- Among the given options:
- Element 32 (Germanium) is a Group 14 element with higher ionization enthalpy.
- Element 19 (Potassium) is in Group 1, but it is not the lowest.
- Element 35 (Bromine) is a halogen, and halogens generally have high ionization energies.
- Element 87 (Francium) is a Group 1 alkali metal and has the lowest first ionization enthalpy, as alkali metals have very low ionization energies due to their single valence electron.
Thus, the correct answer is (4) 87, corresponding to Francium.