1) Indicar el número de oxidación de cada uno de los elementos en los siguientes compuestos:  CH4
 Na2O
 Cr2O7
2) Oxide los siguientes compuestos (Con cada una de las valencias mencionadas):
BeO (valencia del Berilio +2 y oxigeno -2)
ClO (Valencias del Cloro +1,+3,+5, +7 y Oxigeno -2)
NiO (Valencias del Niquel +2,+3 y oxigeno -2)

Which statement correctly describes the phosphate ion, ? it is composed of one phosphorus atom and four oxygen atoms covalently bonded together, and there is a –3 charge distributed over the entire ion. it is composed of one phosphorus atom and four oxygen atoms covalently bonded together, and there is a –3 charge on the phosphorus atom. it is composed of one phosphorus atom and four oxygen atoms ionically bonded together, and there is a –3 charge distributed over the entire ion. it is composed of one phosphorus atom and four oxygen atoms ionically bonded together, and there is a –3 charge on the phosphorus atom.