Q.vii. What are requirements for the colliding reactant molecules to lead to products?

Step 1. Energy requirement: only collisions in which the combined kinetic energy of the colliding molecules is at least the activation energy $E_a$ can go on to form products; the fraction meeting this is $f=e^{-E_a/RT}$.

Step 2. Orientation requirement: for anything beyond the simplest molecules or ions, energy alone is not enough -- the molecules must also be oriented so the specific reacting atoms/groups face each other, illustrated by $A+C{-}B\rightarrow A{-}B+C$, where only an approach with B (not C) facing A can succeed. …

• Listing only one of the two requirements.
• Treating orientation as relevant only for 'complex' molecules in a way that suggests it never matters for simple …