Where do the elements on the periodic table come from?

The elements' journey began in the first moments of the Big Bang, when our universe was only seconds to minutes old.

The Big Bang model holds that a violent explosion gave rise to the present universe. (Image credit: Getty images)

We all know that the universe contains a vast array of elements, from very light gases like helium to very heavy metals like lead. But where did all the elements come from?

The journey of the elements began in the first moments of the Big Bang, when our universe was only seconds to minutes old. At the time, the entire universe was crammed into a volume millions of times smaller than it is today. Because of the incredibly high density, the average temperature of all matter in the universe was well over a billion degrees, which is hot enough for nuclear reactions to occur. In fact, it was so hot that even protons and neutrons could not exist as stable entities. Instead, the universe was just a sea of ​​more fundamental particles, called quarks and gluons, boiling in a primordial plasma state.

But the Universe doesn't stay that way for long. It's expanding, which means it's also cooling. Eventually, quarks can bind together to form the first protons and neutrons without being destroyed right away. Protons are slightly lighter than neutrons, which gives them an advantage in the initial stages of particle creation. After the Universe was a few minutes old, it was too cold to create new protons and neutrons. As a result, these heavy particles are the only ones the Universe makes (except for rare high-energy interactions in the future).

When the heavy particles finally formed, there were about six protons for every neutron. These neutrons were not stable on their own; their half-life was about 880 seconds. Soon, some of the neutrons began to decay, and the ones that had not yet decayed began to combine with protons to form the first atomic nuclei. Of all the light elements, helium-4, which consists of two protons and two neutrons, has the greatest binding energy, meaning it is the easiest to form and the hardest to break apart. As a result, almost all of these neutrons were used to produce helium-4.

Calculations like this allow cosmologists to predict that the universe began with a mix of about 75 percent hydrogen (which is just a naked proton), 25 percent helium, and a small amount of lithium — which is exactly what astronomers observe.

Stellar nuclear fusion synthesis

The next stage in the emergence of elements had to wait for the first generation of stars, which didn't begin to shine until hundreds of millions of years after the Big Bang. Stars power themselves through nuclear fusion, converting hydrogen into helium. This process leaves a tiny bit of energy behind. But stars have so much hydrogen that they can burn for billions, sometimes trillions of years.

At the end of their lives, stars like the Sun turn to nuclear fusion of helium, converting it into carbon and oxygen before they die as planetary nebulae. This is why carbon and oxygen are so abundant in the universe; after hydrogen and helium, they are the most common elements. In fact, oxygen is the most common element on Earth, although most of it is bound up in silicates to form the ground beneath your feet.

More massive stars — those with at least eight times the mass of our sun — fuse heavier elements in their cores. Especially in the final weeks, days, and even hours of their lives, the most massive stars in the universe produce nitrogen, neon, silicon, sulfur, magnesium, nickel, chromium, and iron.

This is the end point of element formation within stars - their intense energies are capable of producing heavier elements, but to form any element higher than iron consumes energy rather than creates it, so these heavier elements are rarely found in the cores of massive stars.

Elements heavier than iron in the periodic table are created when stars die, and they do so in a variety of fascinating, complex, and spectacular ways. Smaller stars slowly eject material from their nuclear reaction zones outward, which sprays material across their star system. Larger stars explode in supernovas. Both types of deaths leave remnants behind—smaller stars leave behind white dwarfs, which are made almost entirely of carbon and oxygen; larger stars leave behind incredibly dense balls of neutrons, called neutron stars.

Gas from the companion star can be absorbed by the white dwarf, causing it to explode as a supernova. The collision of neutron stars can create a kilonova and release huge amounts of energy.

Regardless, all of these processes involve lots of radiation, lots of energy, and lots of particles flying around at high speeds—in other words, the perfect soup for sculpting new elements. It’s through these catastrophes that the rest of the periodic table came into being.

It is also through these energetic events that these elements fly beyond the boundaries of their parent stars and into the interstellar mix, where they join new gas clouds that eventually merge to form new generations of stars, which continue the element cycle and regeneration, slowly enriching the entire universe.

BY:Paul Sutter

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