Step-by-step explanation:
A substance is able to conduct electricity if it has or contains free electrons.
This also means that larger is the atomic radius of a metal lesser will the force of attraction between its nucleus and valence electrons. As a result, it can easily lose its valence electrons.
Therefore, availability of free electrons is easy in that case.
Also, more is the number of valence electrons a metal contains more is the number of electrons participating in conducting electricity.
Thus, we can conclude that a combination of more valence electrons and larger atomic radius factors is most suitable for increasing the electrical conductivity of metals.