Why are the lanthanoid elements not found in nature in their elemental forms?

Which diagram shows the correct way to represent an ionic compound of magnesium oxide?

Consider this equilibrium: n29) + o2(g) + 2no(c).nitrogen gas and oxygen gas react when placed in a closed container. as the reaction proceeds towards equilibrium, what happens to the rate of thereverse reaction?

Draw two cyclic constitutional isomers of cis-1