Write the electron configurations for Period 1 elements. What is the relationship between the period number and the energy level of the valence electrons?
Period 1 elements consist only of hydrogen (H) and helium (He).
The electron configuration for hydrogen is 1s1.
The electron configuration for helium is 1s2.
The period number indicates the energy level of the valence electrons. For Period 1 elements, the valence electrons are located in the first energy level (n=1). Therefore, the relationship between the period number and the energy level of the valence electrons is that they are the same.