Assumptions and Limitations of Law of Ocatves

Q. Amongst the following, which are the two elements that Newlands placed in the same slot and positioned in the same column with flourine, chlorine and bromine?

1. Cobalt and nickel
2. Cobalt and calcium
3. Nickel and calcium
4. Cobalt and Cerium

Q.

From the symbol ${}_{20}{}^{40}\mathrm{Ca}$ state:

Electronic distribution of Ca.