What happens as periods increase on the periodic table?

Answer 1

the principal energy levels of valence electrons increase.

Answer 2

As you move across a period on the Periodic Table, the number of protons increases, which increases the atomic number. This results in a greater positive charge in the nucleus, leading to an increase in the attraction between the nucleus and the electrons in the outer energy levels. This trend generally results in smaller atomic size and higher electronegativity as you move across a period.