Final answer:
The AsF₃ molecule has four areas of electron density around the central arsenic atom: three from the bonding pairs with fluorine atoms and one from a lone pair of electrons.
Step-by-step explanation:
The student has asked how many areas of electron density there are around the central atom of As in the AsF₃ molecule. In order to determine the regions of electron density, we must consider both bonding pairs and lone pairs of electrons. Arsenic (As) has five valence electrons, and each fluorine (F) atom has seven valence electrons. When we draw the Lewis structure for AsF₃, we see that As will be the central atom, with three F atoms surrounding it. Each F atom will form a single bond with As; thus, there will be three regions of electron density from these bonding pairs. Moreover, since As started with five valence electrons and three are used in bonding, that leaves us with two electrons or one lone pair. Therefore, the total areas of electron density around the central As atom will be four: three from F atoms (bonding pairs) and one from a lone pair.