Urgent In a single replacement reaction, why do atoms of a pure element substitute in ion in the compound it is combined with?

I also need help with this one

You are to give ampicillin with a recommended dose of 25mg/kg to a child with a mass of 29kg. if stock on hand is 250mg/capsule how many capsules should be given?

Which of the dna typing techniques do you think you would choose if you had to analyze a dna sample? why?

How many valence electrons are in atom of radon?