Sulfur (S) is an element with atomic number 16. Its electronic configuration is [Ne] 3s2 3p4.
In sulfur trioxide (SO3), sulfur forms covalent bonds with three oxygen (O) atoms. Each oxygen atom contributes 2 electrons to form a total of 6 shared electrons in the three sulfur-oxygen bonds.
To determine the number of valence electrons in sulfur in SO3, we consider the lone pair electrons on sulfur and the shared electrons in the sulfur-oxygen bonds.
Sulfur has 6 valence electrons (from the 3s and 3p orbitals). In addition, each oxygen atom contributes 2 electrons, resulting in a total of 6 x 2 = 12 electrons from the oxygen atoms.
Since there are three sulfur-oxygen bonds, we count 6 shared electrons from the sulfur-oxygen bonds. Therefore, the lone pair electrons on sulfur in SO3 are given by:
Valence electrons in sulfur = Total valence electrons - Shared electrons - Electrons from oxygen = 6 + 6 - 12 = 0
So, in sulfur trioxide, sulfur does not possess any lone pair electrons or valence electrons. It has utilized all of its valence electrons to form bonds with the oxygen atoms.