Answer: Correct option is (D).
Step-by-step explanation:
Given that unknown element has larger atomic radii than potassium atoms and its valence electrons feel an effective nuclear charge of +1 which means that this unknown element belongs to group(I) of the periodic table.
In periodic table:
- As we move down the group the value of ionization energy decreases down the group. This is due to increase in the size of an element.With increase in size valence electrons gets far away from the nucleus by which less energy will require to ionize the element.
- Electronegative characters also decreases when we move down the group.This is due to increase in size of an element by which electrons present in valence shells are far away from the nucleus.
So,It would have lower ionization energies than K and a lower electronegativity value than K.