On the periodic table, each element is assigned an atomic number. Besides showing its placement on the periodic table, the atomic number shows the number of protons located in the center of the atom. In this case since the element has 5 protons in it, then its atomic number is five. Using this information, you can also find out other information about the element.
Since you have the number of neutrons in this element which is 5 and the atomic number, you can add those numbers together to find the mass number of the element. Dmitri Mendeleev is known for creating the periodic table. He organized the elements based on the weight of each atom. Over time more elements were added to the table as they were discovered.