Which answer choice correctly describe a trend of valence electrons in the periodic table?

Select all that apply.

Elements in the same group have the same number of valence electrons.
When moving right across a period, the valence electrons of the main group elements increase by one.
When moving down a group, the valence electrons of the main group elements increase by one.
Elements in the same period have the same number of valence electrons.

Explanation:

Even though elements in the same group have the same number of valence electrons, the valence electrons get further away from the nucleus further down you move in the group. This is because more orbital shells are being added in each period. This makes the elements at the bottom more reactive because the valence electrons are shielded form the nucleus and are easily dislodged in a reaction.

When moving right across a period, the valence electrons of the main group elements increase by one and get closer to the nucleus as they are attracted more to the nucleus due to the increasing mass number as you go right across the period. The elements to the left of the period are more reactive becaue they have less valence electrons to lose to achieve a stable configurations. Also their valence electrons are not strongly attracted to the nucleus due to the relatively lower proton number in the period.