Methyl chloride (CH3Cl) has a tetrahedral shape with a bond angle of 109.5 degrees. This is because carbon has four valence electrons forming four bonds and in a three-dimensional space, a tetrahedral shape allows for the bonded electrons to be furthest away from each other.
Molecular shapes are predicted using the valence shell electron pair repulsion theory (VSEPR). According to VSEPR, molecules will have a geometric shape that allows their negative charge centers (bonded and lone pair electrons) to be as far away from each other as possible, due to the mutual repulsion of the negative charges. Molecules with two negative centers tend to be linear (a bond angle of 180 degrees in a two-dimensional plane). Molecules with three negative centers are trigonal planar (bond angles of 120 degrees in a two-dimensional plane), and molecules with four negative centers are tetrahedral (bond angles of 108.5 degree in a three-dimensional space).
Methyl chloride has a central carbon atom surrounded by four single bonds (three to hydrogen and one to chlorine). Therefore, according to VSEPR, the molecule will have a tetrahedral shape with a bond angle of 108.5 degrees to allow maximum separation of the bonded electrons.