Which element can expand its valence shell to accommodate more than eight electrons? which element can expand its valence shell to accommodate more than eight electrons? o he n br?

Br can expand its valence shell to accommodate more than eight electrons.

Explanation:

In a bond, elements tends to accommodate their valence electrons to reach the configuration of a noble gas (The Octet rule), so they try to complete their valence shell with 8 electrons, and they can do that only if they use the orbitals s (may contain only 2 electrons) and p (may contain only 6 electrons).

Sometimes, there are elements that need to share more than 8 valence electrons to use all the available electrons, but this is possible only if the atom has orbitals d (may contain 10 electrons) or f (may contain 14 electrons).

That's why only the elements that has a number 3 of period or more can expand its valence shell, because level 3 atoms has a d subshell.

In this case, He atom is in period number 1, N atom is in period number 2 and Br atom is in period number 3, that's why Br atom can expand its valence shell, and He and N atoms can't.