Question

when moving across a period from left to right in the periodic table (excluding transition elements) which trend occurs? (1 point) valence electrons increase by one. the energy levels increase by one. the energy levels decrease by one. valence electrons decrease by one.

Explanation:

As you move from left - to - right across a period (excluding transition elements) in the periodic table, the number of protons in the nucleus increases by one, and the number of valence electrons also increases by one. The energy levels remain the same for elements within the same period.

Answer:

Valence electrons increase by one.