How many neutrons does hydrogen have? how many neutrons does carbon oxygen?

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?

Nan element’s square on the periodic table, the number with the greatest numerical value represents the

What methods could you use to solubilize calcium carbonate