The "aufbau principle" says that electrons fill the lowest energy orbitals first, which means that level one orbitals get filled before level two orbitals, which get filled before level three orbitals, and that within each level the s orbitals get filled before the p orbitals. So, there are ...
By definition, each element has one more proton than the previous element - so element 1, hydrogen, has one proton in the nucleus, while element 2, helium, has two protons in the nucleus. The periodic table represents elements in their atomic form, where there are an equal number of proto...