Question

Because the first energy level contains only the 1s sublevel how many elements are located in the first periodic

Answer 1

There are 4 types of orbitals. The s, p, d and f orbitals. They can contain a maximum of 2, 6, 10 and 14 electrons, respectively. So, for the 1s energy level, you would expect a maximum of 2 electrons. That includes elements 1 and 2, hydrogen and helium. These are the only 2 elements in the first period.