Answer: Ionic formula will be 
.
Explanation: 
and 
ions will form a ionic compound. Ionic compounds have both metals and non-metals.
Here is a metal and is a non-metal.
The net charge on any compound must be 0.
So we need 2 phosphate ions to balance the charge on ions. Similarly we need 3 Magnesium ions to balance the charge on ions.
Criss-crossing the charges, we will get the formula as
Criss-crossing is shown in the image below.
Answer:
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BY CHECKING THE REACTIVITY OF AN ELEMENT WHICH IS MOST REACTIVE OR NOT AND YOU STUDY TYPE OF CHEMICAL REACTION IN 1 CH AND YOU CHECK THE REACTIVITY OF ELEMENTS IN 3 CH METALS AND NON METALS PAGE NO 45 IN NCERT BOOK
Answer:
I would say A and D if you can pick two answers. if not then pick D
