Both of Mercury’s valence electrons are in the atom’s 6s shell. An electron in the outermost shell of an atom is a valence electron. Valence electrons can bond with the valence electrons of other atoms to make a compound.
You can figure out how many valence electrons mercury has by looking at how its electrons are set up. The configuration of the electrons is shown as 1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2. The energy level is shown by the first number in each section. The farther away the orbital is from the centre of the atom, the higher the energy level. In the sixth energy level, the shell type is shown by the letter s, and the number two shows that there are two electrons in the outermost shell.