a) Lightest metalloid is boron.
The metalloid are boron, silicon, etc. We know the size increases as we move down a group. So, all other metalloids are larger than boron.
b) explain again.
c) Mp of sulphur is 386.36 K and that of sodium is 370.87 K.
Reason---- It is the van der Waalsâ forceswhich is responsible for the low melting point of sulphur. when sulphur melts, the van der waals forces between the molecules are broken. These are very weak bonds. So, little energy is needed to overcome them.
We hope that clarifies your query.