The best and the poorest conductors of heat are respectively

Thermal conductivity is the property of a material to conduct heat. Among all metals, silver (Ag) possesses the highest thermal conductivity, approximately 429 W/m·K, making it the most efficient conductor of heat [1]. Copper (Cu) follows silver as the second-best conductor. Conversely, lead (Pb) and mercury are identified as comparatively poor conductors of heat among metallic elements [1]. Lead has a significantly lower thermal conductivity compared to silver, copper, or aluminum, which is why it is often cited as the poorest conductor in the context of common metals. While gold (Au) is a good conductor, it is less efficient than silver and copper. Therefore, the pair representing the best and poorest conductors respectively is silver and lead [1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > List the metals whose wires you have seen in daily life. > p. 38