Order the elements carbon, oxygen and chlorine from the ff:

1) greatest to least according to atomic radius
2) greatest to least according to ionization energy

And ff is what?

Your answers can be found here.
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/trends.htm

To order the elements carbon (C), oxygen (O), and chlorine (Cl) from greatest to least according to atomic radius, we need to consider the trends in the periodic table.

1) Atomic radius trend:
Atomic radius decreases as you move across a period from left to right and increases as you move down a group.

Carbon (C) is positioned to the left of oxygen and chlorine in the periodic table. Therefore, it has a larger atomic radius than both oxygen and chlorine.

Oxygen (O) is found to the right of carbon and has a smaller atomic radius than carbon.

Chlorine (Cl) is located further to the right of the periodic table and has the smallest atomic radius among these three elements.

So, the order from greatest to least atomic radius would be:
Chlorine (Cl) > Oxygen (O) > Carbon (C)

2) Ionization energy trend:
Ionization energy generally increases as you move across a period from left to right in the periodic table and decreases as you move down a group.

Carbon (C) has the least ionization energy among these three elements since it is the farthest to the left in the period.

Oxygen (O) has a higher ionization energy than carbon because it is to the right of carbon in the periodic table.

Chlorine (Cl) has the highest ionization energy because it is located furthest to the right in the period.

So, the order from greatest to least ionization energy would be:
Chlorine (Cl) > Oxygen (O) > Carbon (C)