We call these letters symbols. And an element is a pure substance made from only one type of atom. And there are quite a lot of elements. There are something like 100, and each has a unique symbol ...

The symbol for magnesium is Mg, and sulfuric acid is a compound containing sulfur, oxygen, and hydrogen. Its formula is written: H2SO4. So we write Mg plus H2SO4. An arrow shows the direction of ...