I'm a little surprised that you're using Baidu (a Mandarin site) for a question in English,but here goes:
When an atom loses an electron to become a cation (e.g.Be -> Be2+,Li -> Li+),the atomic radius,AKA size,decreases - this makes sense because now the proton:electron ratio has increased so the 'pull' on each electron is stronger.The reverse applies for atom -> anion (F -> F-) as there are now more electrons than protons so the attraction each electron experiences is weaker,thus they are able to spread out further.Does this make sense?
Now we look at the periodic table.
H is in period 1
Li,Be and F are in period 2
Cl is in period 3
The larger the period,the more 'shielding' occurs - so all else being equal the atom in the larger period # must be larger as the outermost electrons experience less attraction.
So the largest is Cl-,because it is (1) an anion and (2) in the largest period.
Among Li+,Be2+ and F-,F- is an anion - so it is the largest.
Then we have Li+,Be2+ and H-.All these have only 2 electrons,which to say shielding is the same (2 electrons = 1 electron shell).So we compare the # of protons:
Li = 3 protons
Be = 4 protons
H = 1 proton
So with regards to size,H- > Li+ > Be2+
And therefore,Cl- > F- > H- > Li+ > Be2+.This is in DESCENDING order.Make sure you fill it in correctly for descending v.ascending.