The Lewis dot structure for H2SO4, or sulfuric acid, features sulfur at the center surrounded by four oxygen atoms. Two hydrogen atoms attach to two oxygen atoms. The elements are abbreviated by their chemical symbols listed on the periodic table of elements, and electrons shared between them are denoted by small dots. These electrons are called valence electrons.
Sulfur, or "S" in the Lewis structure, is surrounded by 12 electrons. Four oxygen atoms, indicated by "O" in the diagram, align on all four sides of the S. Two of these oxygen atoms have six electrons surrounding them, and the other two have eight electrons. Two hydrogen atoms, or "H," attach to two oxygen atoms on opposite sides of the diagram. Hydrogen has two shared electrons on each atom.
Two groups of four electrons are shared between sulfur and the two oxygen atoms that do not have hydrogen attached to them. The other two oxygen atoms share two electrons with sulfur. On the outermost edges of the oxygen atoms, there are no valence electrons. Sulfur has six valence electrons, oxygen has six for each atom, and hydrogen just has one for each atom.
Valence electrons combine with other atoms to form molecules in the outer shell. They are either given up to other substances or shared with other atoms.