Answer:
1)Na2O
let the valency of Na is x
2(x)+(2)=0
2x+2=0
2x=-2
x=-1
2)ZnO
let the valency of Zn is x
x+2=0
x=-2
3)Al2O3
let the valency of Al is x
2(x)+3(2)=0
2x+6=0
2x=-6
x=-3
4)MgO
let the valency of Mg is x
x+2=0
x=-2
The word that is in an incorrect place in the chart is HAIL.
The state of matter of hail is not plasma; hail is a solid at room temperature. Plasma refers to the state of matter in which an ionized gas have approximately equal number of positively and negatively charged ions. Thus, plasma is an ionized gas. Plasma is considered to be the fourth state of matter. <span />
The statement is false because endothermic reactions have a positive enthalpy change, because heat is being added to the system because it requires more energy to react
