Identify the three elements `A, B and C` from the data given below
a. The elements have successive atomic numbers
b. `A` forms a stable anion, `A^(ɵ)`
c. `C` forms a stable cation, `C^(o+)`

Explanation

Let the atomic number of `A` is `Z` and `B` must be `(Z+1)`
and `C` must be `(Z+2)` since, `A, B and C` have succesive atomic numbers.
Halogens form the most stable halide anions as their octet is complete. But in halogens `Cl^(ɵ)` is the most stable.
Whereas alkali metals form the most stable cations.
The atomic number of `Cl=17`
`:. A= "Chlorine" (Z=17)`
`B="Argon"(Z=17+1=18)`
`C="Potassium" (Z=17+2= 19)`
`17,18 and 19` are successive numbers.