Why is there not a corresponding drop in ionization energies between Bi and Po in the sixth period as N and O? and why is there not a corresponding drop between Ba and Tl is the sixth period even though they are in the same group as Be and B?

See explanation

Explanation:

According to the Journal of Chemical Education, Volume 80, No.8 (2003); "The first ionization energy of bismuth appears to be  anomalousIt has been claimed that spin– orbit coupling by the Russell–Saunders scheme would lower  the ground state of Bi+ ..."

However, the involvement of  d and f orbitals in Bi and Po implies that the outermost orbitals are poorly screened hence the drop between nitrogen and oxygen is not observed between Bi and Po.

The same argument could be extended to explain the reason why  there not a corresponding drop between Ba and Tl is the sixth period even though they are in the same group as Be and B.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms