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 ...

Symbol: A one or two-letter abbreviation used to represent the element. Atomic number: The number of protons in the nucleus of an atom of the element. These rules help in identifying and writing ...

Each ammonia molecule contains one atom of nitrogen and three atoms of hydrogen. We know this because the hydrogen symbol has a subscript three after it, whereas the nitrogen symbol has no number ...