Which of the following bonds is the weakest?

The forces acting between noble gas atoms are

Which among the following molecules exhibits strong London forces?

Covalent compounds have low melting points because:

What is the cause of metallic luster?

$PBr_{5(s)} \rightarrow PBr_{4}^{+} + Br^{-}$
$Br^{-} + Br_2 \rightarrow Br_{3}^{-}$
Which of the following forces is responsible for the interaction of $X^{-}$ and $X_2$ to form a coordinate bond between $X^{-}$ and $X_2$?