group 16 elements, also known as the chalcogens have 6 valence electrons, and hence they can achieve noble gas configuration either by gaining 2 electrons or by sharing two electrons i.e., by forming M2- ions, or forming two covalent bonds. The oxidation state of elements is defined as the number of electrons gained or lost to form a bond and its sign is the indication of ionic charge on the element. Oxygen is the most electronegative element after fluorine. The difference in electronegativity between metals and oxygen is generally very high. We know that ionic bond is formed when the difference in electronegativity of any two elements is very high. Thus, metals and oxygen combine to form a metal oxide with oxygen attaining O2- form, so the oxidation state of oxygen is mostly (-II).
Explicación: Ya que en una reacción química no puede descubrir ningún cambio en masa total de las sustancias que en ella intervienen, pues en una reacción química ni se gana ni se pierde masa.
