Yes, phosphorus can form a positive ion in an ionic compound. An example of a positively charged phosphorus compound is the phosphonium ion (PH+4), which is a cation in which the phosphorus atom has lost four of its valence electrons. This can occur when phosphorus reacts with highly electronegative elements, such as chlorine, to form compounds like phosphorus trichloride (PCl3) or phosphorus pentachloride (PCl5). Here the phosphorus atom is bonded to chlorine atoms through ionic bonds where it has acquired a positive charge (P+3 and P+5 respectively).