Short answers, pulled from the story.
The sulfate ion is a polyatomic anion consisting of one central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. Its empirical formula is SO4 with an overall charge of negative two. The sulfur atom is in the plus six oxidation state and each oxygen is in the minus two state.
Gilbert Lewis provided the first modern description of sulfate bonding in 1916, framing it in terms of electron octets around each atom. Linus Pauling later proposed an alternative involving d-orbital pi bonds, which sparked a prolonged debate in chemistry.
Sulfate is the spelling recommended by IUPAC, the international chemistry standards body. Sulphate is the traditional spelling used in British English. Both refer to the same anion.
Magnesium sulfate as a treatment for seizures during pregnancy, a condition called eclampsia, was first reported in 1916. By 1930 it had largely replaced earlier treatments including opioids and contributed significantly to reducing maternal mortality.
Sulfate aerosols produced by burning fossil fuels cool the atmosphere by reflecting sunlight, and accounting for this effect is essential to accurate climate modeling. Paul Crutzen's 2006 proposal formalized the idea of deliberately injecting sulfate aerosols into the stratosphere as a solar geoengineering method to offset warming. Hundreds of studies examined the approach by the early 2020s, though notable uncertainties remain.
Various forms of calcium sulfate were used as building materials since the Bronze Age. In ancient Egypt their use is documented from the third millennium BC, including at sites such as the ruins of Amarna. Chemical identification of sulfate salts as a distinct group did not occur until the 17th century.