Final answer:
Curved arrows in chemistry depict the movement of electrons during reactions, with full arrows indicating a pair of electrons and half-head arrows for single electrons. They are useful for visualizing reactions like the heterolytic cleavage in tert-butyl chloride or the electron transfer forming calcium chloride.
Step-by-step explanation:
Curved arrows are a notational tool in chemistry used to illustrate the movement of electrons during chemical reactions. A single curved arrow indicates the flow of a pair of electrons, whereas a half-headed curvy arrow, also called a fishhook, indicates the movement of a single electron, such as in free radical reactions. In the example given with tert-butyl chloride ((CH3)3C-Cl), the curved arrow from the C-Cl bond to the chlorine atom denotes the heterolytic cleavage of the bond, with both electrons from the bond moving to the more electronegative chlorine, forming a chloride ion with a lone pair and leaving behind a tert-butyl cation (a carbonium ion). This movement often results in the creation of new formal charges, which should always be calculated and indicated if non-zero.
In the formation of calcium chloride from calcium atoms and chlorine atoms, the transfer of electrons would be illustrated by arrows starting from the Ca atom to each Cl atom, showing the movement of two electrons to each chlorine, resulting in the ionic compound CaCl2.
In summary, curved arrows are essential for understanding electron transfer in chemical reactions, such as the formation of ionic bonds, the creation of free radicals, and electron reorganization in molecular reactions. These illustrations assume the reaction is proceeding in one direction under the specified conditions. However, some reactions can be reversible, which is not depicted by the standard curved arrow.