Why All Helium Has Not Escaped Earth’s Atmosphere
[caption id="attachment_14665" align="alignright" width="440"] Hydrogen or Helium?[/caption] Ninety of the elements occur in nature. The smallest and lightest of the elements is hydrogen. Yet, it is abundant in Earth. Almost no hydrogen gas escapes Earth’s atmosphere. This is partly because hydrogen is reactive and exists almost exclusively in combination with other, heavier elements. Helium, too, is a gas. It is the second lightest element. However, it is neither reactive nor abundant. It does not occur in nature in compound form. Why doesn’t it all escape Earth’s atmosphere? Comparing Hydrogen and Helium Although hydrogen is the lightest element and atom, it almost never exists, even as a gas, in atomic form. It assumes, not monatomic form, H, but diatomic form, H₂. The weight of that is twice the weight of an…