Question

Write Lewis structures for \(\mathrm{SeF}_{4}\) and \(\mathrm{SeF}_{6}\). Is the octet rule satisfied for Se?

Short answer

In both \(\mathrm{SeF}_{4}\) and \(\mathrm{SeF}_{6}\), the selenium (Se) atom is surrounded by more than 8 electrons, abiding by the octet rule as elements from the third period can accommodate more than eight electrons in their valence shell.

Step-by-step solution

Lewis Structure for \(\mathrm{SeF}_{4}\)

The total valence electrons in \(\mathrm{SeF}_{4}\) are provided by 1 Se atom (6 electrons from Se) and 4 F atoms (7*4=28 electrons from F), summing up to 34 electrons. Create the initial skeleton structure of Se atom in the center surrounded by four F atoms. Deduct 8 electrons for forming four single bonds (Se-F), which leaves 26 electrons. All remaining electrons will be placed as lone pairs. First complete the octet of surrounding F atoms. Each F atom now requires 6 electrons to complete its octet, using up 24 electrons. The remaining 2 electrons are put on the Se atom, which brings the total around Se to more than 8, which is okay because it can accommodate more than an octet.

Lewis Structure for \(\mathrm{SeF}_{6}\)

The total valence electrons in \(\mathrm{SeF}_{6}\) are provided by 1 Se atom (6 electrons from Se) and 6 F atoms (7*6=42 electrons from F), summing up to 48 electrons. Set up the initial skeleton with Se atom in the center surrounded by six F atoms. Deduct 12 electrons for forming six single bonds (Se-F), which leaves 36 electrons. All remaining electrons will be placed as lone pairs. First complete the octet of surrounding F atoms. Each F atom now requires 6 electrons to complete its octet, using up all 36 electrons. The Se atom has exactly 12 electrons around it in this structure (more than an octet), which is fine since Se can have more than eight electrons.

Evaluate Octet Rule for Se

In both Lewis structures, the central Se atom has more than eight valence electrons. This does not violate the octet rule, as Se belongs to the third period of the periodic table, and elements in the third and higher periods can accommodate more than eight valence electrons due to availability of d-orbitals. Hence, the octet rule is satisfied for Se in both \(\mathrm{SeF}_{4}\) and \(\mathrm{SeF}_{6}\).