Secrets you did not know about the eye-dazzling ingredient, gold

Why is gold golden?

The splendor of minerals has always enchanted humans, fought wars, conquered continents, and led expeditions to prolific and dangerous forests, all to possess the eternal mineral, which is gold. On a note that does not appear to be related to the subject, special relativity tells us that nothing can move faster than the speed of light, and this theory is not only for the speculation of physicists and astronomers, but we must also admire it because its effect on us is closer than we think, and it is surprising that the brilliance of the brilliant yellow gold that Blind mankind by his vicious greed that results from Einstein's special theory of relativity and the dual nature of electrons, and before we discover what makes gold golden, we must first understand what makes it shine.

Why do metals shine?

The answer would be simple: light is reflected off surfaces, but minerals are not. Rather, it is related to very small particles that dance to the rhythm of light.

We know very well that minerals have excellent conductivity of electricity and heat, and these qualities are possible thanks to the loosely linked electrons that move freely around the nucleus with a positive charge, and when a lot of metal atoms come together to form a mineral, a cloud of negatively charged electrons is produced that can move freely, and scientists call it A sea of ​​electrons.

Light - which is an electromagnetic wave and a form of energy - travels in conjunction with an electromagnetic field. When it collides with a metal, the magnetic field creates a ripple in a sea of ​​electrons, the electrons absorb energy from the light and vibrate at the same frequency as the light that absorbed its energy. The energy absorbed by most minerals corresponds to the ultraviolet spectrum of magnetic field waves.

When the charged particles interact with each other, they produce a field, in which case the pool of negatively charged electrons moving by the action of light creates an electric field, and to keep the total charge of the metal zero, the electrons produce a second light wave (if not, we would have felt a small shock each time we touched a shiny metal).

The second wave of light reflected from the metal reaches our eyes and makes the metal appear shiny, and the reflected light is a mixture of wavelengths of all colors in the visible spectrum in different proportions, and this gives the minerals their grayish-white luster, except for gold, copper, and cesium.

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Einstein's Relativity and the Gold Atom

Gold is the element number 79 in the periodic table of the elements and carries the symbol Au, and its nucleus is made up of 79 neutrons with 79 protons, which makes it very heavy and dense, and as a result the nuclear charge - or the positive charge affecting 79 also of electrons - is high, and the electrons must exert a high effort to avoid Falling onto the core due to electrostatic attraction.

Based on Bohr's model of the atom, the electrons move around the nucleus in orbits, maintaining certain amounts of kinetic energy to avoid being attracted to the nucleus, as happens if you attach a stone to a thread and spin it at a certain speed, the stone will maintain a certain distance from the center, but the moment you stop, The stone will either fall circularly to the center or fall.

The electrons revolve around the gold atom at about half the speed of light (1.6 x 10 ^ 8 m / s), and here the relativistic effect interferes, according to the theory of special relativity (energy parity with the product of mass times the square of the speed of light E = mc2), when the velocity of any particle approaches The speed of light begins to gain mass, so the mass of the electrons increases by approximately 20%.

This increase in mass shrinks the path that the electrons take to orbit around the nucleus, and this path is known as the Bohr radius, given by the following equation:

We see in this equation that the radius of Bohr (a0) is inversely proportional to the mass of the electron (me), if one of the two quantities increases the other decreases. The decrease in the Bohr radius and the increase in the electron mass due to the relative constriction is what makes the gold shine yellow with our eyes.

However, a peek at the element table will tell you that there is a missing link in this story because many metals (mercury and lead) are heavier than gold, but their luster is silver. To explain this paradox, we need a savior for every missing link in science fiction movies, Quantum Mechanics!
Dynamic Duality: Special Relativity and Quantum Mechanics

With the advent of quantum mechanics, scientists' view of the color of gold has changed. According to the quantum model, electrons are only quantum particles on which both wave and particle natures appear, and they are found in a probability cloud, and this electronic cloud of atomic orbit gives us information about the probability of an electron in a certain region in space. For example, on a bicycle, the electron would determine the path to only one street, while the quantum model would allow it to reach anywhere in a particular zip code.

Now, going back to relativity, we see that the effect is similar because we see the relative contraction here as well. The atoms have orbits with different shapes (s, p, d, f). S orbit is spherical in which electrons are exposed to the most intense attraction from the positive nucleus.

As a result, all of the s orbits in the gold atom close to the nucleus, and the 6s orbit farthest from the gold nucleus shrinks by approximately 17%.

The convergence of s orbitals closer to the nucleus reduces the attraction of other orbitals that expand away from the nucleus. This reduces the distance between the last 6s orbit and the penultimate 5d orbit.

When light falls on gold, the sea of ​​electrons absorbs that energy, and the gold atoms absorb precisely the amount needed to jump from the lower 5d orbital to the higher 6s energy orbit, and since these two orbits are closed due to relative constriction, the electrons absorb less energy than they normally would in such transitions.

The energy absorbed by the gold atoms belongs to the blue and violet region of the visible spectrum instead of the ultraviolet region, so the second wave reflected by the mineral consists of each The colors are in the visible spectrum, except for blue and violet, and the visible wavelengths that reach our eyes belong to the green and red region, and when these two are mixed, yellow is produced!

Conclusion

The effect of Einstein's famous energy equation on the luster of gold does not end. It also prevents gold from interacting with environmental factors so that it remains pure forever. Gold's ability to introduce visible light and reflect ultraviolet and infrared rays has made it an essential part of space suits, such as a mask. It is very important in satellite components due to its electrical tolerance and resistance to corrosion caused by ultraviolet rays and x-rays.

And the next time someone says that special relativity does not affect our daily life, just remind them that it keeps our jewelry shiny and GPS working.