What are people made of?
Mostly water but also... fat, bones, muscle, organs, hair, skin, nails... all kinds of fun stuff.
But what are those things made of?
At a microscopic level, those things are made of MOLECULES...
Did you know... we were only able to see molecules directly for the first time in 2009, with an advanced electron microscope.
MOLECULE is the general term used to describe any atoms that are connected by chemical bonds. Every combination of ATOMS is a MOLECULE. A compound is a molecule made of ATOMS of different ELEMENTS. All compounds are molecules, but not all molecules are compounds. Hydrogen gas (H2) is a molecule, but not a compound because it is made of only one ELEMENT. Water (H2O) can be called a molecule or a compound because it is made of hydrogen (H) and oxygen (O) atoms.
There are two main types of chemical bonds that hold atoms together: covalent and ionic/electrovalent bonds. Atoms that share electrons in a chemical bond have covalent bonds. An oxygen molecule (O2) is a good example of a molecule with a covalent bond. Ionic bonds occur when electrons are donated from one atom to another. Table salt (NaCl) is a common example of a compound with an ionic bond. Metallic bonds occur between metal atoms.
Each ELEMENT is characterized by a unique number of PROTONS at the center of its ATOM, which is called the NUCLEUS. The NUCLEUS may also contain NEUTRONS, and these particles are surrounded by a comparatively vast electron cloud.
For example, HYDROGEN has ONE PROTON in its NUCLEUS, whereas HELIUM has 2 PROTONS in its NUCLEUS.
It is the number of PROTONS in an atom's nucleus that determine which element it is. This is called its Atomic Number.
The number of NEUTRONS determine the ISOTOPES of each element, that is to say, varieties of each element. HYDROGEN has three naturally occurring ISOTOPES:
PROTIUM has one PROTON
DEUTERIUM has one PROTON and one NEUTRON
TRITIUM has one PROTON and TWO NEUTRONS
See how the number of protons stays the same? Only the number of neutrons change which ISOTOPE of HYDROGEN we are talking about.
We have discovered 118 elements...SO FAR. They are usually depicted in an infographic called THE PERIODIC TABLE. The first 94 are naturally occurring, while the rest have been discovered by science experiments with particle accelerators, also known as atom smashers.
The primary and most abundant element in the universe is HYDROGEN.
The Big Bang created HYDROGEN and some HELIUM in the formation of the Universe.
HYDROGEN exists in vast clouds in the universe, and when there is enough of it and very likely other matter, gravity causes the large and fluffy cloud to collapse and this is what forms a STAR.
Inside the hearts of stars, HYDROGEN atoms are squished together under tremendous pressure and fuse together to form HELIUM.
HELIUM has TWO PROTONS in its nucleus.
HYDROGEN and HELIUM continue to fuse together to form other elements, including those critical for human life.
Cosmologist Carl Sagan said,
"The NITROGEN in our DNA,
the CALCIUM in our teeth,
the IRON in our blood,
the CARBON in our apple pies,
were made in the interiors of collapsing stars,
we are made of STAR STUFF...
We are a a way for the COSMOS to know itself."
The process of nuclear fusion is called, "NU-CLE-O-SYN-THE-SIS" and was suggested by Sir Arthur Eddington in 1920, less than 100 years ago. And, although Dr. Sagan's quote is beautiful and famous, more specifically, different elements are formed in a few different ways.
After HYDROGEN, the next 25 elements up to and including IRON, are basically created in the nuclear fusion process inside stars. I say basically because, the majority of Lithium, Beryllium and Boron (which have 3, 4 and 5 protons respectively) is thought to have been created by COSMIC RAYS breaking up heavier elements. And still other elements are created when larger elements experience BETA DECAY, that is, they run low on energy and become unstable, and begin to lose ELECTRONS.
Elements heavier than IRON (26 protons) are created when a SUPERMASSIVE STAR burns through all of its fuel and collapses under its own weight and then explodes as a SUPERNOVA!
There is another type of stellar explosion which is called a KILONOVA or R-process supernova, which is smaller than a SUPERNOVA and occurs when two neutron stars or a neutron star and a stellar mass black hole merge into each other. There is also something called a HYPERNOVA which has higher than usual kinetic energy. These and other massive explosions can fuse heavy elements as well.
PEOPLE are made from ELEMENTS created in these ways:
We are made of HYDROGEN, which was created in the Big Bang, about 10%.
We are made of 25 other ELEMENTS forged in the hearts of stars, mainly OXYGEN, CARBON, NITROGEN and CALCIUM. Together with HYDROGEN - those five ELEMENTS make up 99% of our bodies. The rest - such as LITHIUM, ALUMINUM, and IRON, are only present in trace amounts.
And we also have within us 22 other ELEMENTS which were created by supernovae - such as COPPER, ARSENIC, ZIRCONIUM, TIN, IODINE, GOLD, LEAD and URANIUM.
Not all ELEMENTS are included in people. From the hearts of stars, we do not contain NEON, ARGON, or TITANIUM (unless, like me, you have a bone fixed with a titanium implant), OR HELIUM (unless we inhale a party balloon :)