It is found to be of sensory function. In most scorpions, it has mechano-receptors which is hypothesized to help the male choose suitable substrate for depositing spermatophore and sense surface vibrations. In some species, it is found to have some contact chemoreceptors. It is one of the most convenient means of determining sex. of some species. Some wonder why the eyes are not included as part of the external morphology.
Reason is simple.
Besides the central eye group in the picture above, there may be a lateral eye group in the anterior lateral part of the prosoma. Also note that the chelicera is not its mouth but an appendages to aid feeding and grasping of food. Used to grasp and crush prey before sucking it. Curiously, it does have an abduction muscle which is absent in the pedipalp. Pattern and shape is used extensively in differentiating the families.