How many electrons do all halogen atoms need to fill their outer energy level?

Seven

Explanation:

Because all halogens have seven valence electrons, they are “eager” to gain one more electron. Doing so gives them a full outer energy level, which is the most stable arrangement of electrons. Halogens often combine with alkali metals in group 1 of the periodic table.

Halogens only need one electron to complete their valkance shells.

Explanation:

Halogens are present in the VIIA group of the periodic table so seven electrons are already present. one is needed to become stable.

the diagram which shows forces as either balanced = same speed or unbalanced = accelerarting