In ionic compounds they positively charged ions are formed from blank elements

How can the number of core electrons be determined from the periodic table

What is the final temperature after 840 joules is absorbed by 10.0g of water at 25.0c

Acompound containing nitrogen and oxygen is decomposed in the laboratory and produces 1.78 g of nitrogen and 4.05 g of oxygen. part a calculate the empirical formula of the compound.