<span>A </span>chemical formula<span> is a way of expressing information about the proportions of </span>atoms<span> that constitute a particular</span>chemical compound<span>, using a single line of </span>chemical element<span> symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and </span>plus<span> (+) and </span>minus<span> (−) signs. A chemical formula is not a </span>chemical name showing how the atoms are arranged.
Ammonia isn't an element, it's a compound made by mixing the elements Nitrogen and Hydrogen in the Haber process. Therefore, it isn't on the periodic table
