The Lewis structure of SiF3- and SiF3 consists of a central silicon atom bonded to three fluorine atoms and an extra lone pair of electrons. SiF3 has a larger bond angle than SiF3-.
The Lewis structure of SiF3- consists of a central silicon atom bonded to three fluorine atoms and an extra lone pair of electrons. The structure of SiF3 is the same, but without the extra lone pair.
In both cases, the bond angle is determined by the arrangement of the atoms and lone pairs around the central silicon atom.
The larger bond angle will be found in SiF3, as the additional lone pair on SiF3- will repel the bonding pairs, causing them to spread out slightly, increasing the bond angle.