Question: how many protons and electrons are contained in each polyatomic ion?
Answer: To calculate the number electrons in the ion. First, add one to the number of protons to find the number of electrons for each negative charge on the ion (-3 ion, add three electrons etc.). For example, NO−3 has: N = 7 protons; 3 O = 3 × 8 = 24 protons; Total = 7 + 24 = 31 protons.