Which of the following could be added to 1.0 liter of 0.10 M HC2H3O2 (Ka = 1.8 x 10^-5) to form a buffer solution with pH between 4 and 5?
1. 0.050 mol HCI
II 0.050 mol NaOH
III. 0.050 mol NaC2H:02
a. I only
b. II only
c. I and II only
d. II and III only
e. I and III only

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.