Origins of metals

In this article you are going to learn about the origin of metals. To do that, we need to go back to the early beginning of our solar system.

All elements in the periodic table are created within stars. At the beginning of its life, a star only consists of hydrogen (H). After billions of years of accumulating hydrogen, energy within the star causes the fusion of hydrogen atoms to helium (He). This process is called nuclear fusion. It goes on during the entire lifetime of a star and it is also able to form the elements Beryllium (Be) and Carbon (C) from the newly formed helium atoms.

However, to be able to create additional elements in the periodic table with higher masses, more energy is needed. This energy becomes available when most hydrogen within the star has fused to helium since energy is released during nuclear fusion. At that point, the star enters a dying stage. During this stage, the star contracts and temperatures in the star begin to rise, releasing even more energy, and producing bigger and heavier elements. Over a prolonged time of element formation, the steady core of a star starts to lose its stability and starts to grow into a red giant. Red giants become increasingly unstable with time and will eventually explode, the explosion of a red giant is what we call a super nova and the ultimate event of element creation.

Figure 1: The process of nuclear fusion of hydrogen nuclei into helium nuclei.

Super novas blast all their contents away in the universe and leave a huge dust cloud of stardust behind in space. From these dust clouds, new solar systems are born containing all the elements that were created in the previous star. Therefore, when Earth formed out of stardust and rock debris about 4,5 billion years ago, it already contained all elements available. The more material that clumped together, the bigger the gravitational pull became, and even more rock debris and stardust was attracted to the core of rubble that soon would be able to classify as a planet. Within the stardust, rock debris, and colliding asteroids, metals heated due to the violent formation processes and formed a core consisting of iron and nickel.

Figure 2: Planet formation from stardust that is left by a super nova.

If all elements were stable, you would expect that the lightest elements would be the most common ones, and the heaviest the least common because they would be the last to form. However, not all elements are stable. Beryllium for example is one of the first elements to form during nuclear fusion but will fall apart soon after its formation. Iron on the other hand is one of the last elements to form in a red giant but is much more stable.

Elements can fall apart in different ways: they can fall apart by emitting a stable He nucleus, which we call an alpha particle, they can fall apart by releasing an electron, which we call a beta particle, or they can fall apart by the release of nuclear energy via gamma rays. We call this radioactive decay. Some elements decay only once, before they become stable elements while others need more steps. The time covering the decay ranges from seconds to millions of years between elements. Therefore, the composition of the solar system and the availability of certain elements on Earth is ever changing.

Without radioactive decay, life on earth would not be possible because it heats the planet from within. In this way, the metals in your mobile telephone, solar panels, and car batteries, are connected to the origin of the universe.

Figure 3: The three radioactive decay processes alpha beta and gamma with their symbols and decay products.