- 2377 - ATOM - defining the atom All the other elements in the periodic table above hydrogen and helium were created in the nuclear fusion of the stars The first stars formed with only hydrogen and helium. When they burned all their fuel and exploded as supernova they splattered the surrounding space with all the atoms in the higher level elements.
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---------------------------------- 2377 - ATOM - defining the atom?
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- The atom is the smallest particle that characterizes a chemical element. There are 118 chemical elements in the Periodic Table and each one has a different atom. When the ancients invented the atom they characterized it as the smallest indivisible part of matter.
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- Later it was discovered that the atom was composed of even smaller “indivisible” parts. Atoms are composed of electrons, protons and neutrons. A neutral atom has the same number of protons and electrons, and there is a different number of protons and electrons for each element. The number of neutrons in the atom does not change the element but makes it a heavier isotope of that same element.
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- Electrons are fundamental particles they can not be divided into smaller parts. They are so small their size is considered immeasurable, but less than 10^-18 meters.
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- Protons are 1,836 times more massive than electrons. In 1961 it was discovered that protons and neutrons themselves were not fundamental particles but were in fact made up of still smaller particles called quarks.
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- In addition, it was discovered that the electron has a nearly massless , neutral partner called a neutrino. Together the electron and the neutrino are called “Leptons“.
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-------------------------- Protons have 2 up quarks and 1 down quark.
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-------------------------- Neutrons have 1 up quark and 2 down quarks.
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- The electrons are bound to the atom’s nucleus by ”photons“, the carriers of the electromagnetic force. Protons and neutrons are bound inside the nucleus by “Gluons“, carriers of the Strong Nuclear Force.
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- The nucleus of the atom is surrounded by a cloud of electrons. The positions of the electrons around the nucleus are described by using statistical probabilities. The shape of the orbital probabilities depends on each energy level the electrons are occupying.
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- Each orbit can hold 2 electrons, each with opposite spin. Higher energy shells can hold more electrons and are located farther from the nucleus. Each shell can hold (2*n^2) electrons, where “n” is the number of the shell.
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- The electrons in the outer most shell are the “Valence Electrons“. The Valence Electrons give the atom the chemical properties of each element. For example: helium has its outer shell full with 2 electrons so it is chemically neutral and does not easily react with the other elements. Hydrogen on the other hand has only 1 electron in its outer shell and hydrogen reacts with most every element it encounters.
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- For electrons to move between shells, to change state, they must absorb or emit energy in the form of photons.
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- For protons or neutrons to change state they become radioactive. Energy emitted in radioactivity can be in the form of protons, electrons, positrons or gamma rays. When protons and neutrons change state it requires 1000 times more energy than when electrons change state.
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- Atoms are 1.06*10^-10 meters, or about 10.6 nanometers in size. This is much smaller than the wavelengths of light which are 600 nanometers in size. Therefore we can not see atoms with an optical microscope.
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- The proton itself is only 10^-15 meters in size, or 100,000 times smaller than the atom. If the atom was a football stadium the nucleus would be the size of a marble on the center of the 50 yard line. The electron is smaller still. If the atom were the size of the Earth the electron would be less the 10 centimeters in diameter, the electron is less than 10^-18 meters in diameter.
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- At room temperature atoms making up gases in the air are moving at an average speed of 1,100 miles per hour. Since each element has its own set of electrons and energy levels, each element creates its own light emission /absorption pattern, its own unique spectral signature. The emission colors and the absorption gaps are called spectrums, and are unique for each element. Their spectrums are not limited to visible light but cover the whole electromagnetic spectrum from radio waves to X-rays.
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- In just 1 millionth of a second after the Big Bang quarks clumped together to form protons and neutrons. After a hundred seconds protons and neutrons gathered into bunches consisting of two protons and two neutrons. Eventually these bunches captured two electrons to form helium atoms and each single proton captured a single electron to form hydrogen atoms. That was it, almost no higher level elements were formed with the Big Bang.
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- Within 3 minutes after the Big Bang all atomic material in the Universe was created. Hydrogen makes up 92% of the atoms in the Universe ( by number, not by weight ), helium 7%, and the rest only 1%. After 379,000 years the Universe had cooled to 3,000K and the nuclei were able to capture electrons and to become neutral.
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- Neutral atoms can only absorb photons at their discrete absorption levels. Therefore, most of the photons were free to expand with the Universe’s expansion. Today the expansion is 1000 times bigger and those photons have cooled by 1000 times, to 3 degrees Kelvin . Today we can detect these photons as Cosmic Microwave Background radiation.
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- All the other elements in the periodic table above hydrogen and helium were created in the nuclear fusion of the stars The first stars formed with only hydrogen and helium. When they burned all their fuel and exploded as supernova they splattered the surrounding space with all the higher level elements.
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- The next stars that formed had these higher level elements in them. They too exploded at their death and created even more higher level elements until we have the periodic table we have today. The atoms in your body are star dust from these repeated explosions..
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- The atoms are small. A single tear drop contains 2*10^21 atoms, (2,000,000,000,000,000,000,000 atoms), of oxygen and 4*10^21 atoms of hydrogen (H2O).
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- An E.Coli bacterium contains 100,000,000,000 atoms. A single hair from your head contains 100,000,000,000,000 atoms. The width of a human hair is 1,000,000 carbon atoms wide.
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- The number of atoms in 12 grams of coal is 6*10^27. I won’t write that out in 27 zeros, but to say that number is 1,400,000 times larger the age of the Universe in seconds.
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- Other Reviews about atoms:
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- 2333 - Rainbows can tell us what the Universe is made of. Introduction to the science of spectroscopy.
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- 2318 - Brownian motion from atoms you can not see.
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- 2315 - About how atoms were first discovered.
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- 2307 - How small is the atom?
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- 2255 History of the atom.
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- 2256 Atom’s stability and uncertainty?
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- 983 - How an atom works? All the math formulas.
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- 985 - Measuring how an atom works?
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- 924 - Rutherford’s atom. How the atom was discovered in 1911.
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- May 23, 2019 753
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--------------------- Friday, May 17, 2019 -------------------------
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