Magnesium oxide Magnesium oxide Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of and consists of a lattice of Mg ions and O ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + HO → Mg(OH)), but it can be reversed by heating it to separate moisture. Magnesium oxide was historically known as magnesia alba (literally, the white mineral from magnesia – other sources give magnesia alba as MgCO), to differentiate it from "magnesia
U Should've Known Better backbeat, the song's instrumentation consists of screeching guitars and an understated harp pattern. Lyrically, Monica, as the protagonist, delivers a message of loyalty to her imprisoned love interest and sings about staying down for him despite his doubts. The song was generally well received by contemporary music critics who highlighted the heartfelt emotion and sadness. Released as the fourth and final single from "After the Storm" in May 2004, the single marked Monica's first balladic release in over five years. On the charts, "U Should've Known Better" peaked at number 19 on the US "Billboard" Hot 100 and number 6