Which of the following pairs of properties of alkali metals decreases down the group?

A. First ionization energy and reactivity
B. melting point and atomic radius
C. Reactivity and electronegativity
D. First ionization energy and melting point

Correct Answer:

Option D – First ionization energy and melting point

Explanation

– The ionization energy of an atom is the amount of energy that is required to remove an electron from a mole of atoms in the gas phase:

– It is possible to remove more electrons from most elements, so this quantity is more precisely known as the first ionization energy, the energy to go from neutral atoms to cations with a 1+ charge.

– The ionization energy decreases from top to bottom in groups, and increases from left to right across a period.

– The boiling and melting points decrease as you move down the group.