Why are the outermost electrons lost easily down the group?

The outermost electrons are farther away from the nucleus

The correct answer is option 4. The outermost electrons are farther away from the nucleus.

As you move down a group in the periodic table, additional electron shells are added, leading to an increase in the distance between the outermost electrons and the nucleus. This increased distance weakens the attraction between the positively charged nucleus and the negatively charged electrons. Consequently, the outermost electrons are less strongly attracted to the nucleus and are easier to remove, resulting in a decrease in ionization energy down the group.

Therefore, option 4 is correct because the outermost electrons being farther away from the nucleus reduces the attractive force between them and the nucleus, making them easier to lose as you move down the group.