There are 92 naturally occurring elements; only 17 of them make up 99.5% of the earth’s crust (including oceans and atmosphere). In living things (plants, animals, people) the six most abundant elements are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. The universe is dominated by the elements hydrogen (83%) and helium (16%)
1. The Crust
The outside of the earth is a thin crust that is approximately 20 to 40km thick. The crust is a formation of dips and hollows which are filled with water to form the oceans and seas. On top of the earth’s crust is an atmosphere, this is a thin layer of gases, 95% of these gases are within the first 20km of the earth’s surface.
Of the 17 elements that make up 99.5%, the most abundant of these are Oxygen 49.2%, Silicon 25%, and Aluminum 7.5%. Then the next most abundant elements are Iron 4.7%, Calcium 3.4%, Sodium 2.6%, Potassium 2.4%, Magnesium 1.9%, Hydrogen 0.9%, titanium 0.6%, Chlorine 0.2%, Phosphorus Manganese and Carbon are all 0.1%, Sulfur 0.05% Barium 0.04%, Nitrogen 0.03% and the rest of the elements on the periodic table take up about 0.5%.
The elements of the crust are graphed below, but only ones that are the most abundant due to the fact that the abundance of the other elements of the crust are too low to graph accurately on one graph.
Almost all elements are found as compounds, however Oxygen, Nitrogen, and to a lesser extent sulfur, gold, silver, and platinum are the only elements that can be found in almost their raw state. The atmosphere contains Oxygen and nitrogen, but it only contains a small portion of the earth’s oxygen, this is because most of the world’s oxygen is found in water, oxides of metals, and silicates. Common soils and clays are silicates.
2. Living Things
In living things (plants, animals, people) the six most abundant elements are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (known as CHONPS). Most compounds in living matter are radically complex; each molecule could contain hundreds or thousands of atoms. Carbohydrates and fats are compounds that contain carbon, hydrogen, and oxygen only.
Proteins are also compounds and they contain nitrogen, sulfur, and occasionally phosphorus. Living matter cannot live on these six elements alone; even though they make up 99% of the mass, they also need some compounds of other elements such as calcium, potassium, sodium, magnesium, iron, zinc, fluorine, and others. These elements are required as compounds so that livings things can use them.
3. The Universe
The universe is dominated by the elements hydrogen 83%, and helium 16%. Other elements in the universe are oxygen 0.1%, carbon 0.03%, nitrogen 0.01%, silicon magnesium, and neon are all about 0.003% of the elements in the universe. The abundance of hydrogen and helium in this cosmic distribution of the elements proves all the elements were formed by nuclear fusion in the stars, for example, the Sun. Hydrogen is a basic material for which the other elements are gradually built.