Reference—Organic reaction mechanism conventions

An organic mechanism should show charges, bond polarity, lone pairs and curly arrows that track electron-pair movement. Curly arrows start at an electron source and end at an electron-deficient atom or bond.

Use a full step only when it changes connectivity: identify the nucleophile/electrophile, show the intermediate and restore charges and octets in the product.

In a nucleophilic substitution, draw the arrow from the lone pair on the nucleophile to the carbon and the C–leaving-group bond to the leaving group.

A curly arrow does not mean an atom moves; it represents a pair of electrons, and it must not start from a positive charge with no electron source.