Final answer:
Out of Potassium, Chlorine, Francium, and Astatine, Chlorine is the most electronegative. Electronegativity increases across a period from left to right and from bottom to top of a group in the periodic table. Chlorine lies above and to the right compared to the others, indicating a higher electronegativity.
Step-by-step explanation:
The element among the ones listed that is the most electronegative is Chlorine. Electronegativity is the tendency of atoms to attract electrons when forming a bond. In the periodic table, electronegativity generally increases as you move from left to right across a period and as you move from the bottom to the top of a group. Based on these trends and known electronegativity values, Potassium (K) has a lower electronegativity because it is in the first group and prefers to donate an electron rather than attract them. On the other hand, Francium (Fr) and Astatine (At) are less electronegative than Chlorine (Cl) because they are to the left and below Chlorine in the periodic table.
Chlorine has an electronegativity value comparable to that of oxygen and is much higher than that of Potassium, Francium, or Astatine. Thus, Option 2: Chlorine is the correct answer here.