Consider the Oxides XO₂,where X Is One of the First

Consider the oxides XO₂,where X is one of the first 20 elements.Identify X in each of the following cases:
a.XO₂ is a natural component of the atmosphere,whose buildup is implicated in climate change.
b.XO₂ is a toxic,brown gas which is a serious air pollutant.
c.XO₂ is a colorless,toxic gas formed during the combustion of coal.
d.XO₂ is network solid;the element X itself is also a network solid.