Which of the following pairs of properties of alkali metals decreases down the group?
- First ionization energy and reactivity
- melting point and atomic radius
- Reactivity and electronegativity
-
First ionization energy and melting point
The correct answer is: D
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.