Earth made up of 90 elements

There are around 90 naturally occurring elements found on Earth. I say “around” because neither technetium nor francium have ever been found in isolatable quantities. On the other, there is some evidence plutonium might be available in some uranium deposits.

This points out one of the fundamental facts about the composition of our planet – the distribution of elements is quite diverse.

The atmosphere is mostly nitrogen (78.09 per cent) and oxygen (20.95 per cent) by volume. Argon makes up 0.93 per cent and was discovered when scientist liquefied the other two gases from air. There was always a small residual amount of gas left in the container no matter what they did. This is where argon derives its name as it was considered “too lazy” to condense as a liquid.

Carbon dioxide makes up most of the remainder of the atmosphere (0.04 per cent) but the other noble gases (helium, neon, krypton, xenon, and radon) are present in trace amounts along with gases such as nitrous oxide and chlorine. There are even natural trace amounts of hydrocarbons.

These concentrations are for dry air and do not take into account the amount of water vapour in the atmosphere which can vary significantly. It averages about one per cent at sea level and 0.4 per cent for the entire atmosphere but can reach four per cent when raining.

The atmosphere doesn’t contain large quantities of iron, silicon, or other minerals. It is made of light gases.

The oceans, on the other hand, are dominated by water. As are streams, lakes, and glaciers and anything else we would consider part of the hydrosphere. There are other elements present in water due to erosion. Minerals such as sodium chloride and magnesium carbonate contribute the saltiness of the salt water bodies.

More rare elements, such as gold, can be found in trace quantities as there is about four kilograms in every cubic kilometre. It doesn’t sound like a lot but when you consider the volume of the oceans is 1.322 billion cubic kilometres, the total is 5.3 billion kilograms of gold. By any measure, that is a lot of gold.

So why don’t we mine the oceans? There are two difficulties. The first is a cubic kilometre of ocean is a lot of water and we do not have an efficient process for extracting the gold as a consequence. The second is each cubic kilometre of sea water contains 13.7 million tonnes of salt. Isolating the gold would require sifting through all of that salt. The good news is the salt could be disposed of by simply putting it back into the ocean.

The Earth’s crust is where we find all of the elements but again the concentrations vary significantly. The crust is dominated by oxygen at 47 per cent, followed by silicon, aluminum, iron, magnesium, calcium, potassium, and sodium.

These eight elements make up 98 per cent of the rocks and minerals we see around us.

While there are 90 or so elements available on Earth, how they are distributed and how they are used varies significantly by where they are located.